Understand the memoir genre. In a memoir, you are the main character of your own life story. Many memoirists use the facts of their life story to create an engaging tale for the reader. Because you are relying on your own memories as source material for the story, you may end up describing things differently than others might remember it. The key is to write down things as you remember it, in the most honest way possible. Keep in mind memoirs are different from autobiographies in that memoirs should only cover certain key aspects of your life, not your life from birth until the present day.
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.