Meditate and become introspective well before the interview. Figure out why you really want to go into medicine. It's a long path with personal sacrifices all along the way, so doing it just to make mom and dad happy ain't gonna cut it. For the "tell me about yourself" question, start off with a good generalization (not overly detailed), then focus on why you are unique (leave out the part about collecting toenail clippings as a hobby). Talk about your passions and what you have learned from them. For example: I run ultra-marathons, and they have truly formed me into the person I am through training, focus on a future goal, and overcoming difficulties. Have a good idea of world events, healthcare issues, and details about the particular school. Have dinner with one of the students if possible. Most importantly, be honest. If you don't know the answer to a specific question, admit that aren't familiar with the details. If you can, put your higher thinking powers to use and forumulate a possible explanation, but don't B.S.
Good luck to you!