Decide where the story is going to start. You could a straightforward chronology of your life, beginning with your birth and ending in the present, but mixing up the chronology can make the story more interesting.
You could frame the entire autobiography with reflections from the present, telling your story through a series of flashbacks.
You could begin the story with a poignant moment from your childhood, go backward to tell the story of your heritage, move forward to your college years, and launch into the story of your career, with anecdotes from your childhood sprinkled in for comic relief.