You should be able to find some useful advice in the Step 1 section of this site. I did not particularly shine on Step 1, but I'm willing to throw in my $0.02 nonetheless. You'll hear about First Aid (FA) for Step 1 ad nauseum during the next 2 years. Some will praise it, while others will say it's not worth the paper it's printed on. That said, I think it's hard (virtually impossible, quite frankly) to find any single source that, word for word, is as high-yield as FA for Step 1. It would be a good idea to purchase this early in your Med School career and review it, though you'll want the most current version when you take Step 2, presumably in 2008. The new editions are usually available around December of the year before, so you may want to wait until December of 2006 and, again, purchase the new 2008 version in 12-2007. (It's updated annually, based on examinee feedback). One of the most highly touted sorces besides FA is Board Review Series (BRS) Pathology. I thought it was OK, but highly over-rated. Some of the other sources which I recommend to others include: High-Yield (HY) Pharmacology, HY Microbiology, HY Neuroanatomy, HY Behavioral Science. I thought some of the other HY books, while useful, were not quite as high on my list of must reads. These include HY: Molecular Cell Biology, Biochemistry, Immunology and Embryology.
I think you'd be better off going with the HY series than BRS as they're shorter and easier to master, which is the key. I thought HY Neuroanatomy was great, as the Neuro in FA blows and the Neuro question on Step 1 are damn hard, plus they have way mroe than 5 choices/question in Neuro as each option can be (Left or Right side? Contra or Ipsi lateral?). Makes guessing correctly that much less likely. For Pharmacology, a lot of what Step 1 tests is your mastery of the fundamentals, which deals with the different receptor types, mechanisms of action, etc. I thought HY Pharmacology does an excellent job in explaining this (Chapter 2, I believe).
Step 1 is tough and, as imperfect as the test is, your score will carry a LOT of weight. Even relatively non-competitive fields like Internal Medicine and Neurology use filters to screen applications. Family Medicine, Pediatrics and Psychiatry are, typically, non-competetive enough that most American grads (even with mediocre Step 1 scores) will be able to match into average programs. For the tough fields, like Dermatology, ENT, Neurosurg, Ortho, etc Step 1 is HUGE, especially for those who attend non-elite schools. If you score lower than you hope on Step 1, you maybe able to obtain the field of your choice by doing other things (ie good M3 grades, Research, electives at places you want to apply for Residency). However, until you take the test, focus on doing well on Step 1. Basic science grades are of marginal value, though they are used in selection for Alpha Omega Alpha (AOA), which is the Medical School honor society. M-3 grades do carry more weight, though. Don't let anyone convince you that Step 1 scores are not heavily weighted when programs review Residency applications, b/c it's not true! Good luck!!