As opposed to the above poster I loved IM, but then I want to do med/peds. There is alot to know and it can be overwhelming...I'd review some things that are certain to come up - pneumonias and their tx, chest pain differential & work-up, sob diff & w/u, GI bleeding, etc. Antibiotics are high-yield. You might also want to brush on reading chest x-rays & EKGs...these were things I was commonly pimped on.
Otherwise, you'll see much more on IM and try to read some every night about the conditions your pts have. The book I liked the most was Step-Up to Medicine.