Sometimes people come into your life and you know right away that they were meant to be there, to serve some sort of purpose, teach you a lesson, or to help you figure out who you are or who you want to become. You never know who these people may be (possibly your roommate, neighbor, coworker, longlost friend, lover, or even a complete stranger) but when you lock eyes with them, you know at that very moment that they will affect your life in some profound way.
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.