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The Most Common Mistakes Students Make When Writing

Luke Holm earned bachelor's degrees in English and philosophy from NIU. He is a middle school teacher and a creative writer.

In this article, I address some of the most commonly made mistakes I've found in my students' writing. Hopefully, this help you teach your own students.

In this article, I address some of the most commonly made mistakes I've found in my students' writing. Hopefully, this help you teach your own students.

The Pain of Being an English Teacher

Anyone who spends their nights correcting the same writing mistakes over and over again is a special person. As an English teacher, I know how difficult it is to read through, edit, and analyze a student's essay. For those who don't understand, note the process of grading broken down into a mathematical formula:

If an English teacher has 100 essays to grade (likely all on the same topic) and each essay takes 5 minutes to grade, then that is just over 8 hours of grading for a single assignment.

If these essays are flawless pearls of wisdom, then the task of reading and grading a student's essay is actually quite enjoyable. However, if each essay is riddled with similar mistakes, ones the teacher has noted, corrected, and recorrected again and again, then the task of grading becomes a lot more daunting.

As an English teacher, I obviously teach the conventions of writing. I help my students revise their work to a polished perfection. Yet, I still have students making the same mistakes over and over again, and it's frustrating.

In an attempt to help remedy these recurring issues, I've written this article. The goal of this article is not to provide an exhausted list of the conventions of English, but rather to address some of the most commonly made mistakes I've found in my students' writing. Hopefully, it can be of service to you or your classroom.

Table of Contents

  1. Sentence Structure
    • Simple Sentence
    • Compound Sentences
    • Complex Sentences
    • Compound-Complex Sentences
  2. Punctuation Marks
    • Periods
    • End Punctuation
    • Ellipsis
    • Apostrophes
    • Commas
  3. Quotations
    • Emphasis
    • Dialogue
    • Drama
    • Citing Evidence
  4. Agreement
    • Subject-verb Agreement
    • Verb Tense Agreement
    • Pronoun-Antecedent Agreement
  5. Random Conventions of Writing
    • Indentation and New Paragraphs
    • Transitions
    • Capitalization
    • Sentence Starters
    • Abbreviations and Informal Writing
    • Writing Numbers
    • Commonly Confused Words

1. Sentence Structure

The two main sentence structure mistakes I find are run-on sentences and incomplete or fragmented sentences. When it comes to run-on sentences, read the sentence aloud. Note where you naturally take a breath or pause. Likely, these place are where a punctuation mark should be. If you end an idea, put a period. If you find that your sentence is spanning multiple lines, consider breaking your ideas down into smaller parts, which will be more easily digestible for your audience.

As for the fragmented sentences, I've found the best fix for these mistakes is a basic knowledge of how sentences are formed.

Simple Sentences

A “simple sentence” has a subject (noun) and a predicate (verb + its objects). It expresses a complete thought.

Subject (Noun)

Predicate (Verb)







to the store.

Compound Sentences

You can have a compound sentence with two subjects, a compound sentence with two predicates, or both at the same time.

Subject (Noun)

Predicate (Verb)


Bob and Barb





to the store and the movies.

Bob and Barb


to the store and the movies.

Complex Sentences

Needless to say, a “complex sentence” is a bit more complex. A complex sentence has one part of the sentence that can stand alone (independent clause) and one part of the sentence that cannot stand alone (dependent clause).

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As shown in the examples above, in order to write an independent clause (aka complete sentence), all you need to do is create a subject (noun) + a verb (+ any additional information about that subject or verb). Similarly, a dependent clause is created with a noun and a verb, but a dependent clause does not express a complete thought or idea. It is “dependent” on the other, complete, part of the sentence.

Dependent clauses are oftentimes introduced through subordinating conjunctions. The most common are:

after, although, as, because, before, how, if, once, since, than, that, though, till, until, when, where, whether, and while.

Using these words is a good indicator that you are writing a dependent clause, which will require a second part of the sentence.

Dependent Clause

Independent Clause

Since Bob walked to the store before the movies,

he missed the previews.



Independent Clause

Dependent Clause

Bob missed the previews

after going to the store.



Compound-Complex Sentences

Finally, you can combine compound and complex sentences together, but in order to do this, you’ll need to use a coordinating conjunction (FANBOYS), which I explain below.

Independent Clause + Dependent Clause (Complex)

Coordinating Conjunction (FANBOYS) + Independent Clause (Simple Sentence)

Bob and Barb missed the previews because they went to the store,

but they weren't mad.


2. Punctuation Marks

As you might have noticed, as sentences become more complex, various punctuation marks are needed. The biggest punctuation mark students need help with is the comma, but I've found that even the most basic punctuation mark can be overlooked.

Periods (.)

Students, don't forget the period mark. It's frustrating for teachers when you do. Periods end sentences, which are complete thoughts.

Sometimes, they are used for abbreviations such as Mr. or 10 p.m. If your sentence ends with an abbreviation, you only need one period.

Example: She's the president of Pineapple Inc.

Other End Punctuation Marks (!?)

Here, it should be noted that when using punctuation marks to end a sentence, please only use one. Formal writing is not a text message to your bff. It's not ok to use multiple exclamation marks (!!!) to overemphasize a point. If your question is both exhilaration and inquisitive, stick with the question mark. The audience should be able to read the author's tone through the context of the passage. It's never ok to write (!?).

Ellipsis (. . .)

The ellipsis is a fun punctuation mark for many students. However, most use it wrong. It's written as a space before and after each of three periods. It can be useful; however, students often either include too few/many periods or use it at inappropriate times.

Use the ellipsis when indicating a pause in thought or trailing off of thought in informal dialogue.

Example: If only they had . . . Oh, never mind.

You may also use an ellipsis when quoting part of an outside resource in an essay (the ellipsis indicates information has been taken out of the quote). Note, however, that this technique for quotation is currently in flux, and it is becoming more acceptable to use part of a quote without the ellipsis.

Apostrophes (')


The main mistake I see students make with apostrophes is not knowing where they go in a contraction. I'll see words like "should'nt" or "ca'nt," but the only rule for a contract is to replace the omitted letter(s) with an apostrophe.

Example: haven't / might've / would've

Note: Not all words need an apostrophe. The word "it's" means "it is," whereas "its" without an apostrophe is a possessive pronoun.


While we're on the topic, apostrophes can and do make nouns possessive. Add an apostrophe + s ('s) after a noun to show that it owns something.

Example: Bob's credit cards were declined at the store.

Note: If you have a plural noun such as the word "cards," you add an apostrophe after the s to make it plural. If you have a name such as Chris, you add an apostropher + s after the name to make it possessive.



Commas don't have to be tricky. While poetry is in a class of its own, formal writing only follows a few comma rules.

1. Introductory Phrases

Commas set off transitional or introductory phrases like "However, . . ."

Example: In conclusion, . . .

2. Lists

Commas separate members of a list.

Example: Bob, Barb, and Bill went to the store, the movies, and then back home.

3. Non-restrictive Phrases

Commas set off non-essential phrases or (parenthetical) information within a sentence.

Example: Bob, who looked like a grump, was actually quite jolly.

4. Comma Separates Dependent + Independent Clause

When there is a dependent (subordinate) clause that comes before an independent clause, a comma follows the dependent clause.

Example: Although Bob hurried, he still missed the previews.

If there is a dependent (subordinate) clause that comes after an independent clause, there is usually no comma needed.

Example: Bob cried when he missed the previews.

5. Comma + Coordinating Conjunction

Now's the time to talk about coordinating conjunctions. These words join two similar complete sentences together. Coordinating conjunctions are often called FANBOYS:

for, and, nor, but, or yet, so.

Use a comma before a coordinating conjunction joining two complete sentences together.

Example: Bob missed the previews, but he wasn't mad.

Note: The comma comes before the coordinating conjunction.


3. Quotations

Quotation Marks (" ") for Emphasis

Oftentimes, students will use quotation marks to emphasize a point or a word. Usually, this is unnecessary. Unless what is being quoted is something someone else said, the emphasis of a word or phrase should be found in the tone of the passage.

Dialogue in Literature

Dialogue in literature is punctuated a particular way. Here are a few simple rules all writers must follow.

1. Each time a new character speaks, the author should start a new paragraph.

2. If a speech tag comes before the character's line, the dialogue should be set up with a comma and then capitalized.

Example: Bob cried out, "We've missed the previews!"

3. If a speech tag comes after the character's lines, use a comma in place of what would be the period ending the dialogue. The speech tags should not be capitalized (unless they start with a proper noun).

Note: if the punctuation mark was an exclamation point or a question mark, leave them as they are.

Example: "We've missed the previews," he said.

Example: "We've missed the previews!" he screamed.

Example: "Have we missed the previews?" Bob asked.

Note: Make sure your speech tags are in alignment with what's being said. Questions should be followed with speech tags such as "asked" or "wondered. Also, speech tags such as "yelled" or "screamed" should have an exclamation mark as part of the dialogue.

Dialogue in Drama

Similar to literature, drama has dialogue. However, conversations are written differently in a script than they are in a novel. Here, speech tags (called stage cues) are written in parenthesis and follow the character's name. Stage cues are written in italics, and are typically not spoken by the characters, but are rather directions as to how to act.

Example: Bill (nervously checking the time): I think we are going to be late!

Citing Evidence

Authors use citations when providing examples of evidence to support what they are saying. While there are many ways to quote from a source, a good basic rule is to provide context for the quote and then format it similarly to dialogue in literature.

Example: In Holm's story, "Bob Visits the Movies," he writes, "Bob missed the previews, but he wasn't mad."

Note: Authors can paraphrase information and then use only parts of the quote to support what they are saying. Remember that the fragmented quote can be preceded or followed by an ellipsis (depending on which writing format you are following).

Example: In his essay, Holm notes that Bob "wasn't mad" when he missed the previews.

Finally, authors can add information to a quote using brackets [ ] to help what is being quoted better flow with overall passage or essay.

Example: In "Bob Visits the Movies," Holm notes that "[after] Bob missed the previews..."

Citing Titles

One more note about quotation marks, and that is that is when citing the title of a song, short story, article, essay, poem, or any other shorter work of literature, the title should be put in quotation marks.

If the title is that which comes from a longer work of literature, like a novel, or an album, or an anthology of poetry, then the title should be cited in italics.


4. Agreement

Three common agreement mistakes I see over and over again are subject-verb agreement, verb tense agreement, and pronoun-antecedent agreement.

Subject-verb Agreement

As previously stated, a complete sentence has at least a subject (noun) and a predicate (verb). Simply stated, these parts of the sentence need to be in alignment with each other. So, if your subject is singular, you must have a singular verb. If you subject is plural, you must have a plural verb.

Singular: Bob walks to the store.

Plural: Bob and Barb walk to the store.

Note: Typically, if your subject is plural, then your verb will not end in the letter s. If your subject is singular, then your verb will end in the letter s.

Verb Tense Agreement

Your verbs indicate to the audience the time that events are happening in your story. If your story starts off with, "Once upon a time, . . ." then your story happened in the past, and all the verbs describing your story (except the dialogue) should be in the past tense.

Similarly, if your story is unfolding as the narrator speaks, then all your verbs should be in the present tense (with the exception of dialogue).

Once upon a time, there was a man named Bob. Bob walked to the store with his friends, but this caused them to miss the movie previews.

Pronoun-Antecedent Agreement

Like verbs, pronouns must agree with the noun they are replacing. For example, a male character named Bob could be replaced with pronouns such as "he" or "his," whereas a female character named Barb might be replaced with pronouns like "she" and "hers."

Bob, Barb, and Bill walked to the movie. They were late to it.

Note: You must have a clear antecedent noun that the pronoun agrees with. Without a clear antecedent, the audience will be confused. Imagine if somebody ran into a room and screamed, "Did you see it?" Of course, since no one knows what "it" is (they don't know the antecedent noun), they will be confused.


5. Random Conventions of Writing

As mentioned in my introduction, there is much more to learn about the rules and conventions of writing. Rather than detailing an exhausted list of grammar, this article is a compilation of the most common mistakes I see in student essays and narratives. I've tried to categorize these errors as best I could, but the following mistakes are ones that are a bit more random than the others. They are, nonetheless, extremely important points that all students should know.

Indentation and New Paragraphs

Students, indent the beginning of your paragraphs. Properly using the margin on a piece of paper is a tool that your audience uses to decipher your writing. If you aren't using the margin, then it becomes difficult to see where paragraphs begin and end.

With that being said, create paragraphs! Block writing can be a very frustrating part of any English teacher's job. Stories and essays should not be a single paragraph. Typically, authors start new paragraphs when:

  1. a new speaker begins or adds to a conversation or dialogue.
  2. a scene, tone, or idea changes.
  3. contrasting information is introduced and elaborated upon.
  4. a new subtopic in an essay is being discussed.


While we're on the topic of moving from one paragraph to the next, authors should be sure to use transitions. There are basic transitions such as first, next, or finally, and there are more extravagant transitions such as furthermore, moreover, and likewise.

While all of these transitions have their place, that place is usually somewhere within the paragraphs, rather than at the beginning. If these common phrase transitions are used as movement between paragraphs, the writing begins to sound cliche and mechanical, so try to avoid them.

Instead, the best way to transition between paragraphs (in a formal essay) is to subtly discuss the idea from the last paragraph as an introduction into your discussion for the current paragraph.

Imagine I am writing an essay where the first body paragraph's minor topic is about Bob's calm and collected response to not seeing the movie previews, and the next body paragraph is about Bob's obvious lack of emotion in life. I might write something like:

Even though Bob "wasn't angry" about missing the previews, critics of his character begin to wonder at his mental stability.


One of the most common mistakes I see in students' writing is capitalization, or the lack thereof. Students, please capitalize the beginning of your sentences! Capitalize proper nouns. Capitalize the beginning of dialogue. This is an extremely important start to your sentences. Look at how strange a sentence looks when it's not properly capitalized:

Incorrect: even though bob missed the previews, he wasn't angry.

Correct: Even though Bob missed the previews, he wasn't angry.

Furthermore, be careful not to overcapitalize words. A lot of times, students will capitalize entire words to show emphasis. In a formal essay, this is TOTALLY not acceptable. If you want to add particular emphasis to a word, use an exclamation point at the end of the sentence or provide context to reveal the importance of the world. If you still feel the word is being underemphasized, you can put the word in italics to make it stand out from the rest.


Starting Sentences with Then, So, But, and And

Speaking of starting sentences, one of the worst mistakes I see my students make is repeating the same word or phrase at the start of each sentence. Oftentimes, I'll read stories such as, "Then, the dog went on a walk. Then, the dog sniffed fire hydrant by the grass. Then, the dog lifted its leg. Then, . . ."

Students, most of the time, you will not start sentences with then, so, but, or and. The easy way to remedy this issue is to drop which of these words you are using to start your sentence and go with your next word. Usually, the next word would be a good start to the sentence.

If you are writing what happens in a sequence and find that you have a strong desire to use the word "Then, . . ." over and over again as your sentence starter, trying using other simple transitional words such as, "After, . . ." or "Next, . . ."

If you find that you keep using the word "But, . . ." at the beginning of a sentence, try using "However, . . ." instead. Also, maybe you can combine the previous sentence with the current sentence starting with "But," because "but" is a coordinating conjunction, which joins two complete sentences together.

In any case, whichever words you use to write your essay or story, be sure to use a variety of vocabulary words to get your point across. Don't rely on a thesaurus to write your essay for you, but also don't be scared to mix up your vocabulary from time to time.

Abbreviations and Informal Writing

When writing, be sure to respect the level of formality that different types of writing imply. Obviously, a text message to your best friend is a lot less formal than a college application essay. In any case, it's always best to stay formal unless told otherwise.

This means you should never be abbreviating words (totes vs. totally) or using informal acronyms (LOLed vs. laughed out loud). Be sure to write out the word "to" instead of using the number "2." Don't write "C" instead of "see," or "cuz" instead of "because."

Furthermore, staying formal goes beyond informal abbreviations and acronyms. It's also important to use language that is in alignment with the purpose of the piece of writing. Avoid overusing "like" in formal essays as a means for building emphasis. You shouldn't be starting sentences with, "Like, seriously, . . ."

One more note about staying formal, and that is to avoid using the second person pronoun "you" (or any derivative of the word) in formal essays. You indicates a shift from 1st or 3rd person into 2nd person, essentially breaking the fourth wall. Typically, using "you" is inappropriate in most formal essays. You want to speak objectively, not subjectively. When you say "you," you begin speaking directly to your audience, which usually has no direct involvement with what you are writing.

Speaking informally makes you sound unintelligent to the audience. Really, the only excuse to use informal language in formal writing would be when indirectly revealing character traits through their unique type of dialogue (slang).

Writing Out Numbers

Similarly, when using numbers, it's important to stay formal in your writing. Formal writing has a common practice of writing out numerals zero through ten in word form, and then use the actual number for any numeral higher.

Commonly Confused Words

Finally, there are some commonly confused words that students should note and memorize the differences between. The most commonly confused sets of words are:

  • There: points to a place
  • Their: plural possessive pronoun
  • They're: a contraction of "they" + "are"

  • Where: asks about a place
  • Were: plural past tense of the verb "to be"
  • We're: a contraction of "we" + "are"

  • To: means "toward" or "until"
  • Too: an adverb that means "excessively" or "also"
  • Two: a number

  • Your: a second person possessive
  • Your a contraction of "you" + "are"
  • U R: informal slang or abbreviation for you + are (should not be used in a formal essay)

  • Accept: means to receive
  • Except: means to exclude

  • Affect: a verb that impacts or changes other objects
  • Effect: a noun and the result of a change

  • Its: shows possession
  • It's: is a contraction of "it" + "is" or "it" + "has"

Learn From Your Mistakes

In the end, everyone makes mistakes. However, it's the people who follow the proper conventions of writing that are most easily understood.

If your writing frustrates your audience, or if your writing is too confusing for someone to read, then you will lose your audience, and they will no longer read what you've written. If they give up on your work, then what was the point of writing down your ideas the first place? Writing is our amazing ability to express our thoughts in a clear and systematic way. Without this widespread skill, humanity would still be in the Middle Ages. So, don't act like a peasant. Write well like as scholar.

I hope this article was helpful for you or your students. If there is something I covered that I got wrong, or if there is another common mistake that you see students making over and over again, please let me know in the comments section below.

© 2019 JourneyHolm


John Hansen from Gondwana Land on September 02, 2019:

This article is interesting and helpful. Thank you for sharing.

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