Consider your audience. Think about your professor's teaching styles and the things he has emphasized in the classroom to get a better idea of the things he is interested in. Try to choose a topic for your paper that both you and your professor will enjoy and find exciting.
Focus on what you have been studying in class. For example, if you have been focusing on Charles Dickens' novel, "Great Expectations," you may want to stay away from a thesis that focuses on Shakespeare's "Hamlet" unless you can find a way to relate the work you choose to the work you are studying.
Conduct research outside of the classroom environment while trying to make connections to what you are learning inside the classroom. Find new ways to explore topics that you have been exploring in class. This will help you generate an idea for your thesis.
Choose a thesis statement that allows you to meet the page length requirements and gives you ample information to explore and discuss. Stay away from topics that seem too easy or thesis statements that already have been explored extensively in the classroom.
Revise your thesis if necessary after you have finished your writing assignment. If you are not given a specific topic from the beginning of your writing experience, it is possible that you may change topics throughout the course of your paper. Make sure your thesis statement reflects what you discussed throughout the piece.