As others have noted, talk to your senior classmates and ask them about their experiences on each rotation - what the expectations are, whom to avoid and whom to spend time with (if at all possible), etc.
For surgical rotations, have a pair of bandage/trauma shears - invaluable in taking down dressings.
For all rotations, have a penlight available and extra pens, because your residents will often not have one in their pockets.
Contact the service intern or junior resident (not the Chief - for some reason here, the academic contact person tells the student to page the Chief resident on each service for info - a great source of consternation for them) and find out where, when, what the wear, the schedule for the week (do you have clinic duties? if so, can you wear scrubs, or do you have to wear "street clothes"?). Show up early, especially if you aren't familiar with the hospital, parking etc.
Briefly review the pertinent chapters in your textbooks - don't try and read everything for the rotation before you start.
If on a rotation with OR time (ie, Ob-Gyn, and Surg) check with the OR as to the schedule for the day you start. Most will have a tentative list printed up the Friday before you start - that way you can check and see what cases you might possibly see the day you start.
