I think it's best to start at the beginning of your life...after all, in telling about yourself these early times in life have often defined who you are today. Did you grow up in a "traditional" family atmosphere? Rural or Urban setting? What was your family life like back then? What did you learn from your family life at a young age that has influenced decisions you made during middle/high school? Then progress into motivating factors throughout these years that later led you into choosing your major in college. What activities did you engage in during college? What makes you tick now, as opposed to when you were young?
I find it easiest to develop, before the interview of course, a story that highlights family life, influences, interests...a story that begins at birth. Just make sure you include why you have chosen medicine. It's really hard to come up with a story of your life that can be reiterated in 10 or so minutes. What I did was sit down and write a few important things about my family life, how the rural setting influenced my individuality, and what my motivations were throughout high school and college. Take a couple of hours and try to do this. Then, the night before the interview, review your notes and tell the story to yourself or a friend (I mostly told them to myself as none of my friends travelled with me on my interviews). This way it's fresh in your mind.
Also, include some things that might strike further conversation with the interviewer...often these things are best to conclude with..things like what types of food do you enjoy, are you a sports finatic, books, hobbies, etc. I know this takes time, but believe me...it makes the interview process so much easier. I have been asked this question at 7 different schools (a couple of times I was asked this same question from all three interviewers at the school - both closed file schools), so it's definately one to be prepared for. Hope this helps, and take care.
