Many high-school teachers like to assign personal statements as a writing activity. Not only does this teach students how to write about themselves, but it also comes in handy when they are applying for college. Nearly all colleges require personal statements as part of the application process. Take your time and write a good personal statement in your high-school English class so you can use it for college.
Read the assignments carefully. Personal statements usually ask you to explain an event that changed your life, someone who is important to you or some other cause of personal change. Your assignment will also probably have a length requirement, and may have specific points you're supposed to address.
Decide on the topic. Even if the personal statement asks for the most important person in your life, you don't necessarily have to write on the most important one. Pick something that you can write freely on without feeling the need to censor yourself. If you're not sure what to write about, try writing down your thoughts on a few different subjects. The one that flows the most easily is probably the best.
Write a short, predictable introduction and dive right into the body of the essay. Rather than struggling over the right words to begin the essay with, say something like "This essay is about Mr. Jones, the most important person in my life." This will get you writing. When you're done, you can return and rewrite it.
Tell the story. You personal statement should introduce the subject, develop it and show how you changed as a result. For example, if you are writing a personal statement about a favorite person you might say when you met him, what your first impression was of him, what he did that inspired you and how that changed your life.
Write your conclusion, which is the main point of your statement. A personal statement is always about some change. Whether you're writing about a friendship, an experience or a book, you need to tell the reader how it has made you a different and (hopefully) better person. Don't go into grandiose language; keep it down to earth. If all the experience taught you was to not make snap decisions without thinking something through, then that's what you should talk about in the conclusion.
Redo the introduction. The conclusion goes from a personal experience to a more universal lesson. The introduction should mirror that, going from something universal into your personal experience. For example, if your lesson was the one about not making snap decisions, you might talk about hearing the phrase "look before you leap" from your parents when you were young, but never thinking about it until you had a particular experience.
Get someone else to read through your personal statement before you hand it in. It would be a shame to put in all that effort, only to get marked down for typographical errors or simple grammatical mistakes.