Preparing for USMLE Step 1 is daunting. You know it is the one of the most important test you will ever take, and it will determine what type of residency you will be able to get in to. All that is true, but do not worry too much – with the correct preparation you can do well on Step 1.
As I mentioned before, the most important part of preparing for Step 1 is learning as much as possible and doing well in the first 2 years of medical school. You should give yourself about 4-6 weeks of intense preparation. Any shorter will probably not be enough, and too much longer will make you burn out. Set up a reasonable study schedule before you start and try to stick to it. Here is an example of a good study schedule that I used when preparing for Step 1.

Read a review book. Most people use First Aid for the USMLE Step 1, and I did as well. It is not bad for reviewing much of the high yield material, but do NOT use this as your only resource. It has many mistakes in every edition so make sure to also get to check out the First Aid errata page. I am not sure how much it really helped me on the exam, but I would do it again just to be safe. Supplement your First Aid reading with other, topic specific review books when you don’t completely understand the concepts in First Aid.
The most important thing that you can do is practice tests. Why is this? You can read about how retrieval significantly improves memory in this paper if you want, but the basic idea is that the more you are tested (ie the more questions you do) the better your memory will be of those subjects tested. My personal experience supports those results as I remember the explanations of questions that I have done far better than any other kind of studying.
I used UWorld and tried a friends Kaplan Q-bank, and I can say without a doubt UWorld is much better, and would definitely recommend it. It is more difficult than Kaplan, so you end up learning more from all the questions you missed, and the format of the questions is more like the actual Step 1 exam.
After you sign up for UWorld read my guide on how to best use UWorld Q-bank to study for Step 1. Doing as many questions as possible and reviewing the ones you missed is crucial.
Go to the USMLE website and download their tutorial and practice questions. Go through the tutorial and practice questions that they provide to get an idea of what the test format will be like.
Finally, one to two days prior to the exam you should not do any studying. Just relax, do something that you enjoy, and allow your mind to rest.