Start by writing an outline of your life. Don't leave any detail out. Start from birth and continue to the cut-off age for your autobiography.
Look at old family photo albums to conjure up memories of the past. Sometimes you may forget crucial moments, and reminiscing over old photographs may jog your memory and help you recapture your exact emotions.
Read old diaries or journals. These journals serve as a gateway to your past, allowing you to remember your state of mind as pivotal events were taking place. Also read old letters or emails, and take note of your then-emotions.
Interview your siblings, parents, other family and friends to get different perspectives on your life events. This is good when you can't find the value of a certain event. Talking to others will help you understand the lessons you've learned.
Highlight the 10 most pivotal events in your life. Write out all of the details about these events. Try to capture your emotions, and what impact these moments had on the rest of your life. It could have been a parent's death, the welcoming of a new pet or transferring to a different school. The most important factor is that these moments became catalysts for your life.
Decide on a theme for your autobiography. You can go with a theme of amazing grace, forgiveness, redemption, abiding happiness, patience or others. When you pick a theme, start to find that same angle in all 10 of your pivotal events. Although when you're writing, you're not explicitly giving the moral of the story to the readers, you want to always have in mind the theme you want to convey to your readers.
Read other people's autobiographies. It's great to see how other people have documented their life story, and it may inspire you on your own venture. You don't need to read the whole autobiography, just get a flavor of the writing style and the way the author chooses to tell her story. It would be a good idea to read lots of different autobiographies to get a feel for different writing styles.
Identify your reading audience. Will it be for your children, family, friends or the general public? Are you writing only for yourself, to gain more clarity? The tone of your autobiography will depend heavily on who will read it. If it's to your loved ones, your autobiography may take a more informal tone, but if it's for the general public, you may be careful in how you characterize the different people in your life.
Edit yourself later; write with abandon now. Many people have a tendency to edit themselves as they write. It's easy to write everything that comes to mind, and then go back and cut out of the parts that you don't need after the autobiography is finished.
Be specific. Many writers think that you should just be general, but when you delve into the details, people can draw parallels from their own lives.