If you are just writing for your family, that story might be different than if you were writing your story to be read by the general public. Think about whether or not you want to change people’s names. If your life was a harsh one you may not want to include the real names of the people involved. You may also want to consider whether your life story could be written as fiction. There’s an old adage that “real life is better than fiction.” Maybe your true story could be written in fiction form making it more saleable for mass market.
Stick to informal language, unless it’s absolutely necessary to use formal terms. Instead of “utilize” you can just put “use”. Focus on simple language, with one or two syllable words. The only time you should be using higher level language is if you are using scientific terms or describing a technical process. Even then, you should be writing for the average reader.
Autobiographies are often confused with memoirs. An autobiography is the inspiring story of a person’s entire life and the societal setting thereof, while memoirs have a narrower focus on the narration of a particular span of time within the subject’s lifetime. It mostly deals with individual’s memories, feelings and emotions. Memoirs are generally much shorter in length because they tend to concentrate on a particular theme rather than the entire life of the person. If you’re interested in writing a memoir, this is a great course to check out.

It was only when Sophie’s husband accused her of giving birth to another man’s baby that she went for paternity tests and discovered that her husband was right (sort of). The baby, then aged 10, wasn’t his, but she wasn’t Sophie’s either. She belonged to another set of parents, who had been raising Sophie’s biological daughter in a town several miles away.
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.