I went to a mini seminar on writing thesis statements last night and the bottom line was ANSWER WHY, NOT HOW. A good thesis statement answers the question WHY something happens and makes an argument. Don't rewrite the question either.

:D Hope that helps. I wish I had a copy of the thesis statement he showed us.

He also mentioned that your thesis statement is VERY important. You also want to write something unique. He said picture a reader with a 1ft+ stack of papers. Make sure yours stands out.