Start by writing the story of your life for yourself first. After you edit and polish it, share it with a few trusted people. Then, after you edit and polish it again, share your life story with a wider swath of people. This will help ensure your memoirs are your best possible work, and that your writing is something you’ll be proud of at the end of your life.
Once you have taken a look at your own life from an outsider’s point of view, you will be able to select the most interesting elements from your notes to establish a theme. What was the most interesting thing you came up with in your research? Was it the history of your family and your region? Here is an example of how you can turn that into a theme:
Sometimes people come into your life and you know right away that they were meant to be there, to serve some sort of purpose, teach you a lesson, or to help you figure out who you are or who you want to become. You never know who these people may be (possibly your roommate, neighbor, coworker, longlost friend, lover, or even a complete stranger) but when you lock eyes with them, you know at that very moment that they will affect your life in some profound way.
Capture the spirit of the times. How was your story shaped by the moment in history in which it took place? What wars influenced your politics? What cultural events inspired you? Be sure to include a few important dates so readers can understand the sequencing of the events you are describing. Discussing what happened in the world at large during your lifetime is a good way to make your story more relevant and interesting to those reading it.
People choose to write about their lives for a variety of reasons, including a desire to leave a memoir for their children and future generations, to create a record for themselves so they can be reminded of their youthful adventures when they're old and forgetful, and to offer something of value to the rest of the world. Writing a memoir is a very personal experience, but if you're willing to share your life story, it can be incredibly rewarding.
Why it helps: There’s no need to do the actual examination and investigation now. Instead, just focus on identifying what it is you might delve into someday—in a memoir or in the pages of a journal or just in your mind. What truth is important for you to get at? You have a structure (your three sentences), you have a crucial event (that may have caused or contributed to that life story) and now you have a purpose—a reason for writing that will let you learn, enjoy and even be surprised by the story you’ve been waiting to tell yourself and—maybe, just maybe, the world, as well.
Develop a central theme, main idea or thesis that clearly explains the purpose behind your autobiography. For example, your theme might be about how you overcame obstacles to become a stronger person, or it might explain why a particular passion -- such as mountain climbing or rescuing animals -- is so important to you. Back your theme with details and background information about your life experiences. For example, you might explain that your dad is in the military, so you've had to learn how to adapt quickly to new schools and unfamiliar environments. Or, you might discuss what it was like growing up in a poor, single-parent home, but how your family was always willing to take in injured or stray pets.