The best thing you can do for boards this early is to learn the material well. That doesn't necessarily include learning class material well, though it can. But work hard, and more importantly, smart, your first two years. There are a lot of good lecturers out there that present material in a way very conducive to learning. Some students like Kaplan, some like Pathoma/Sattar, some Goljan, some Najeeb, and various others. I'd say give each of them a try and see what works for you and what you can fit in to your class studying. As for supplements, Costanzo's physiology is great and imo better than BRS for that initial first pass of the material as it flows better, with BRS being better for later passes. Goljan and Pathoma are great for path. With micro, I didn't like CMMRS and loved the Lippincott flashcards, but both are good resources presented in a very different style. These are the only resources I'd highly recommend to supplement the first two years. I didn't find a pharm, embryo, or neuro book I liked enough to recommend. Lippincott's illustrated review for immunology was good, as was How the Immune System Works, though the latter book was overly simplistic and the former too in depth. And anatomy comes down to whatever resource(s) fits your style best. I liked Rohan's and Netters. A copy of FA might be nice to follow along with in your classes in case your lecturers skip anything important or if you like the mnemonics, though it is not an ideal learning tool.
Also, Savarese's book was amazing for OMM. Wish I'd had it first year.
