all u have to do is answer the questions, show u can at least have a thought process if u can't figure one out and keep your cool. the nervous weird thing is prolly what did it. just remember the people talking to you are just people. try to have a normal conversation. dont backpedal, apologize, or stammer. make sure you dress appropriately i.e. no khakis. wear nylons, match ur belt and shoes. wear a suit coat and a tie, pretty basic stuff but someone is always under dressed. dont wear to much perfume. also if you go to the studentdoctorforum.com there is a section about med school interviews there are a lot of science questions there that you'll hear at med proffesional interviews and other tips about what to wear how to act ect. good luck