take excellent care of your patients. don't rely on following your interns by example on everything; oftentimes they are too busy to be able to really get know their patients very, very, well. You, however will probably carry only 3-4 patients (max.). Make use of the extra time.
Read up on the common things that you see; not only on your patients, but other patients as well (SBO, pneumonia, COPD, CHF)... and take some time in the beginning of your clerkship to review your renal, cardiac, and pulmonary physiology.
You may also find that even some attending physicians are weak in pathophysiology... review in Harrison's for each of the common problems you encounter.
The combination of books that I found worked best for me was NMS Medicine and MKSAP (I felt that First Aid was garbage... remember, the majority of material in the series is submitted by students... it's just a big scrapbook of facts and mnemonics). If you're discplined, read all of NMS (it's 400 pages but trust me). If you're not disciplined (like me), do as much of MKSAP as you can early on (these aren't shelf-like questions but still useful); regarding NMS, read as much as you can, but MAKE SURE you do all the clinical cases (9 or so) and the comprehensive examination in the back, and cross-reference the cases and exam with the subject material in the book (DKA, SOB, CP, BIG emphasis on differential diagnosis). NMS is solid stuff... but I only recommend if it you want to really shine in the clerkship and do very well/learn a lot. If you don't care about your grade/what you learn, just use First Aid and cram.
Don't gun. Play hard but be fair. Establish a rapport with your team. If you really work hard and show interest your evals will shine.
Also- stay organized. I used the sheets from scutwork.com and they were amazing.