Any words can be used to start an essay and there isn't really any particular words or phrase that works best. Generally, I tell students to begin a first draft of an essay by setting a timer and just writing down everything they think or know about the paper topic. This does not have to be full sentences. You can write down just words or phrases. After you've written for about 5-10 minutes, stop and re-read what you have. If you haven't yet decided on a thesis question, this is a good time to choose one. The next step is to answer that question, which makes your thesis answer (main thesis statement). From there, you can decide on your introduction, body, and conclusion. I have many different articles on how to write different kinds of essays. You can Google the type of essay you are writing with my name and this website and you can find a full set of instructions.