Develop a central theme, main idea or thesis that clearly explains the purpose behind your autobiography. For example, your theme might be about how you overcame obstacles to become a stronger person, or it might explain why a particular passion -- such as mountain climbing or rescuing animals -- is so important to you. Back your theme with details and background information about your life experiences. For example, you might explain that your dad is in the military, so you've had to learn how to adapt quickly to new schools and unfamiliar environments. Or, you might discuss what it was like growing up in a poor, single-parent home, but how your family was always willing to take in injured or stray pets.
If the project becomes too much for you at any point, remember that writing an autobiography takes time. Take the pressure off. Relax. This is your autobiography. You can make it as brief or as complete as you like, but don't expect to write it quickly. It may take years. If you want to finish fast, you might try the $14.95 Memorygrabber software I mentioned early. The publisher offers numerous free downloadable pages on their website, so you can decide if that approach will be useful or not.
Writing an autobiography for a high school or a college English class can help you gain a deeper sense of personal identity. An autobiography allows you to tell your story in a way that reveals truths about your values, goals and dreams. Though there's no exact science to writing an autobiography, you should include information about your background, major events that shaped who you are and any core themes in your life. Include specific examples to help readers understand your life history.