I started studying around 6 months in advance. I dont know how it'll pay off (as I havent recieved my scores yet), but my NBME's were okay (244 3 weeks out, 251 1 week out).
Personally, I was very weak in all first year material (anatomy, phys, biochem, immuno), so I grilled the anatomy and phys along which each organ system in class.
Then I made sure I didnt forget anything form second year, I reviewed the organ systems from the beginning of the year again and that was priceless.
I started doing World questions about 3 months out and put all my notes into first aid from the questions on little post-it notes. That was okay - but I dont think it was nearly as helpful as reviewing the OS material.
I forgot stuff plenty, but when I went through again during cruch time 5-6 weeks out, it came back real quick, i had my notes, and everything was fresh and familiar. I had my notes organized and there werent any new concepts because conceptually I knew how the nephron worked my first time through during the semester (not OS).
The most most important thing you can do - that I kinda regret not doing more of it myself - is to make sure you learn lecture material damn well so you never forget it, once that's done, do everything else. The main reason I studied early is that I went through all the exam experience threads, and I never saw anyone start studying really early (5 months early +) and not break 230.
That was my strategy.
Dont believe everyone saying "you'll burn out". You know yourself better than anyone else does, if you think you'll be fine, you'll be fine. And on that not, do what works for you - if you learn best when cramming, dont study cram, if you learn best over a prolonged period of time, study early. The best advice I ever got for step 1 review is "do what you know will work for you".
