Things you need to know right off the bat for Peds:
weight and height for different ages - you must know if the kid is developing on schedule or is too skinny, too fat, etc.
immunization schedule
calculate med dosages per weight
good physical exam skills
If you have a shelf exam at the end of the rotation, consider reading "Blueprints in Pediatrics" as you go along. I didn't like it as a reference for wards and clinic but it was good for the shelf exams and Step 2. As for the wards/clinic I would recommend one of the following:
Nelson's Essentials of Pediatrics (it is the "baby" Nelson, nit the big one)
or
Schwartz's Clinical Handbook of Pediatrics
In addition, if your rotation is mostly or all inpatient you will need the Harriet Lane Handbook, which is "the bible" on the pediatric wards. If it is a pediatric outpatient rotation, you will not have much use for it, though.
For FP, there are lots of good books:
University of Iowa Family Practice Handbook
Saint-Frances Guide to Outpatient Medicine (a little watered down, but good for quick ref)
are just the couple that come to mind right now.
Make sure you have ePocrates on your Palm and Sanford's for your selection of antibiotics.
Those are good easy rotations to start your third year with. FP residents and attendings are probably the nicest and most laid back. Peds attendings and residents are way nice to their patients but don't let that fool you, they can be majorly anal with med students (and this advice coming from someone who did 3 peds electives on top of the required rotation).
Good luck and enjoy
