I can't stress enough that the best way to prepare for Step 1 is to bust your ass during your M1 and M2 classes. Step 1 tests basic CONCEPTS, MECHANISMS of disease, and PRINCIPLES of pharm/therapeutics. There is some random minutia that you memorize but this is all short term stuff that is drilled during the 4-6 weeks of boards review before you take Step 1. It would be useless, in my opinion, to try and remember the minutia 10 months before your exam.
You might not realize it, but you are studying for Step 1 when you are attempting to master the basic concepts, mechanisms, and principles during the first two years of medical school. Once you have this stuff down cold, REVIEWING for 4-6 weeks before Step 1 is much easier and you really maximize your score.
If you absolutely INSIST on doing specific step 1 review during the year, the only thing you should really do is review some physiology, cell bio, and biochem that is relevant to the organ system or module that you are currently studying. So, if you are on your cardiovascular module, it would be a prudent to review CV physiology, cardiac myocyte histo, etc. before you started reading robbins, pharm, etc. This way, you refresh your mind with a lot of the 1st year material while really nailing down the 2nd year material. Another thing that helped me out was reviewing some immunology throughout the year while learning micro, since it seems that these subjects inevitably go hand in hand. Again, immunology is chock full of fundamental concepts and would be good to review while you are learning basic pathology and micro.
Basically, learn things right THE FIRST TIME and you'll have a much, much easier time the second time around (i.e. boards review in the spring).
PM me with any questions. Godspeed, M2s!