There is not just one good starting sentence for your essay. However, there are some easy, good ideas for a starting sentence. I usually suggest that students start with one of the following:
1. An example of the problem or situation.
2. A vivid description of the topic.
3. A historical example or current news topic.
4. A personal experience which relates to the issue.
5. A quote that summarizes your point.
Follow up this specific example with an indication of how this applies to a broader audience. Then give the topic question and thesis answer. For more help on how to do this, see my article on how to write a thesis: http://hubpages.com/humanities/Easy-Ways-to-Write-...