Agree that school specific advice would help.
However in general I would look for a few things:
1) Proximity - makes your life a lot easier. There were always a few students who lived far far out from the med center in year one; they almost inevitably moved closer before second year.
2) Safety - you may be keeping weird hours (late nights at the library or anatomy lab); walking or biking or driving home at night you don't want to be worried about safety
3) Convenience - what I mean by this is...is this a place with good landlords, where problems will get taken care of for you easily? Is it close to grocery stores, food options? etc.
4) Cost - everyone has got a budget. I can't tell you what yours is or how much the apartments in your area run, but it has got to be a factor. Don't go over your budget, whatever it is.