Limit it to 15 minutes, no more – at least at first. Fifteen minutes, three times a week, always at the same time and always in the same place. Stay there for all 15 minutes even if you can’t think of anything to write.  This will set up a rhythm, in the same way we get hungry at mealtimes whether or not we’re really hungry. This isn’t just about finding time to write your life story.

What to write: Choose one or more of the sentences below and write a page or two that begins with that particular sentence. Don’t worry about bringing up material that you are afraid might be too painful to explore, says Temes. “Please don’t bother with grammar or spelling or punctuation issues. “Just write for yourself and for your clarity of mind.”
These two sets illustrate how you should show the entire action and then show the entire reaction. Don't mix the two together in one paragraph. Write your entire book in this way — action and reaction, one complete set after another. If one part of the set is missing, readers will sense an awkwardness. If you're writing an autobiography, or anything else, action/reaction sequences will make your writing lively and natural. As you expand your ideas, write in action/reaction pairs.

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.
Writing autobiography can be nerve-wracking that you can barely start a single letter on. But there are also some instances when the story just keeps on flowing that you won’t even know when to stop. With these two cases, just continue on writing your bio and review all the details you were about to get out from yourself after that. In order to be effective, learn first how to write an autobiography of myself by starting with the basic definition of an autobiography.

Identify the main characters. Every good story has interesting characters, friends and foes who help move the plot along. Who are the characters in your life? It's a given that your parents will play a role, along with your spouse and other close family members. Think beyond your immediate family to others who have affected your life and should play a role in your autobiography.
Write out your life timeline. Start writing your autobiography by conducting research on your own life. Creating a timeline of your life is a good way to make sure you include all the most important dates and events, and it gives you a structure to build upon. You can consider this the "brainstorming" phase, so don't hesitate to write down everything you can remember, even if you don't think the memory will make it into the final version of the book.