Conduct basic research. Depending on your story, you may feel you need to do in-depth research on a certain subject, like air force pilots in WWII or life in a refugee camp in Poland. However, resist doing too much research before you start your first draft. You may get overwhelmed by the amount of information you come across during your research and start to forget your personal take on the facts. Remember that your memoir should focus on your memory of the event, rather than be purely factual or completely accurate.
Be revealing. You don't have to be explicit, but it's important to reveal truths about yourself and your life in an autobiography. Don't let the book become a list of your accomplishments, with all the negative material carefully kept under the rug. Present yourself as a whole person, sharing talents and flaws alike, and your readers will be able to identify with you and hopefully root for you as they make their way through your story.
You should check your autobiographical essay for mistakes in spelling, grammar, verb tense, style, punctuation, word forms, etc. No matter how emotional or exciting your writing is, your readers will stop reading as soon as they notice the first grammatical mistake. An illiterate author cannot win the trust of the audience, so you should take this step very seriously.
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.