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.
Many people cannot resist the temptation to tell as much as they can, but a longer piece of writing doesn’t always equal a better piece of writing. For whatever reason you are writing the autobiography, think of the person who is going to read it. Imagine you were an admission officer or the judge in the scholarship committee, and you have to choose from hundreds, if not thousands, of autobiographies. At some point you will hate people who prefer to write long admission essays and autobiographies. There’s also a good way to check whether your writing is interesting or not. Give it to one of your most impatient friends, who prefers short articles to books and long stories, and ask for their opinion.
Create an outline or a graphic organizer of the major topics and ideas you want to cover. For example, you might make a time-order chart -- a chart with event blocks to organize events chronologically. Or, you might draw a cluster web -- a diagram with connected circles -- to divide your autobiography into sections, such as one for relevant background information, one for life-changing events, one for special memories and one for goals and dreams. Focus on reasons why specific events, situations and circumstances were important to you and how they made you feel.