People choose to write about their lives for a variety of reasons, including a desire to leave a memoir for their children and future generations, to create a record for themselves so they can be reminded of their youthful adventures when they're old and forgetful, and to offer something of value to the rest of the world. Writing a memoir is a very personal experience, but if you're willing to share your life story, it can be incredibly rewarding.
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.