Bruce C. answered 06/30/20
Retired Technical Writer and Analyst
Boy, that is a bit of a toughie! If you don't already know how you want to portray yourself.
Because it is a memoir, you might think that it is something you can write without doing any research, but that would not be true! Your memories of some phases of your life, or some incidents, might have faded with time, or might have become idealized in your memory (our memories tend to edit out the bad and keep the good). Other people may have vivid memories of events that your memory has lost or glossed over.
So I would start by interviewing your family members and friends - basically anyone that was close to your during an important period of your life - and recording their memories and perspectives. I also would collect all of the memorabilia, keepsakes, photos, school records, etc. that document the important activities in your life - catalog them and write a short summary of where they fit into your life, what they mean or meant, and why you kept them. Doing so will hopefully stimulate your memory of those events. Finally, write out YOUR memories organized by major periods - pre-school, school, first job, first marriage, first house, first kid, etc.
Then distill the interviews and personal memories down to a few interesting or important periods or events, and structure your memoir around those events or periods. With the first-round interviews and your memorabilia in hand, I would go back to my sources (interviewees) and interview them more intensely about the particular periods or events that you have decided to feature in the memoir. Recounting the memories of others and displaying your souvenirs and keepsakes may draw out additional details. At that point, you should have more than enough "factual" - or at least objective - material to draft a memoir.
I would also work on developing a theme to weave into the memoir. Was day-to-day life satisfying and rewarding, or were you always looking for something over the next hill? Was life a struggle where you overcame obstacles, or did opportunities and accolades just fall into your lap? Was it a dark trek thru a dangerous forest or a sunny safari through an interesting landscape filled with oddities and mysteries? Having a coherent theme running thru the anecdotes and milestones of your life will tie it all together and make it more interesting.
Good luck and good writing!