Weave in themes. Use the major themes of your life as a way to tie stories together, connecting your past and your present. Aside from the central conflict, what themes have followed you throughout your life? A fondness for certain holidays, your fascination with a certain place that you visited over and over, a certain type of guy you've always fallen for, a rich spiritual life you fall back on again and again. Bring up the themes every so often to help form a cohesive picture of your life.
Use chapter divisions to give the book structure. Chapters are useful because they allow you to move on from discussing certain life periods or events. There's a reason we have the expression that we've "closed a chapter" or "opened a new chapter" in life, and it's even more applicable when discussing an autobiography. Chapter breaks allow you to skip forward 10 years, go back in time, or start describing a new theme without jarring the reader too much.
Use simple words and phrases: Think from reader’s point of view. Do not imagine that everybody will know what you know. Readers will be fed up if the story narration demands scrambling for a dictionary each time they come across a big word or surfing the net for new topics that you haven’t described at least in brief. Use only simple words and phrases that everyone can understand, and when introducing a new concept or subject, explain it so they know what you’re talking about.
If you are not sure that your whole life path is worth attention, then a memoir is your best choice. It is focused on one particular event, relationship, place, or period of your life that has influenced your personality a lot. Don’t be afraid to express your personal feelings and ideas in your memoir, as it shouldn’t be simply a brief list of facts, but the reflection of your inner world.
Be revealing. You don't have to be explicit, but it's important to reveal truths about yourself and your life in an autobiography. Don't let the book become a list of your accomplishments, with all the negative material carefully kept under the rug. Present yourself as a whole person, sharing talents and flaws alike, and your readers will be able to identify with you and hopefully root for you as they make their way through your story.
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.
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.