Write down the ending of your memoir first, which includes a climax. This the where the journey of your personal story ends in the memoir and once you decide on an end, you can structure the rest of the events in a linear narrative.
Organize a timeline of important events. Memoirs are about changes, turning points and challenges of a person's life, and write down every event that would inspire others.
Talk to your parents and relatives about your birth and your family's journey before your birth. How your ancestors influenced or didn't influence you may be important to your memoir and this research may work itself into your outline and book.
Write all the events of your life into a coherent linear narrative. Consider adding stories before your birth. Write this down on paper in easy to read lines. You are not writing the book yet. The outline needs the basics and use short sentences as a way to organize the structure.
Examine the outline for a three act structure or another type of story arc. Memoirs are not exactly fiction novels, but they should have all of the same elements of a good story.
Throw out events that are off track to the final climax and end of your story. You want a sense of unity and focus for the entire memoir and the outline stage is the best time to cut out unnecessary elements of your story.