Often, the first draft is not the essay you originally envisioned. You might even discover that your ideas about your theme have changed as you have been writing. If you do not like the way certain sections are stated, re_arrange them. Once you are pleased with the body, make sure the conclusion and introduction still match it and complement the way you see your topic at this point. If not, rewrite them to fit the essay you did write and the way you see your topic now.
When you are sifting through the vast amount of sample you will have access to, be sure that you are looking for samples that will pertain to you and your personal situation. Once you find sample personal statements that you think have helpful information you can print them out and highlight any areas that you feel may help you when you set out to write your own statement. It is also a good idea to take notes as you go along.