1- Mora and more Sample questions:
the most effective way to study for the USMLE is by using professionally developed question banks (like KAPLAN question bank).These question banks focus on the important, tested topics, and are pretty good at identifying distractors (those "wrong" answers that sound pretty believable).
2- Concentrate on your weaknesses:
The USMLE is broken down by topics. That means you have to perform in all the areas to do well on the test as a whole. You know you're weak in an area when you've done poorly in a course - but if you've done well on a school-specific test or in a pass-fail course you can't tell how you'll perform on the USMLE.
3- Study for the USMLE as you study your medical school course:
This seems like a trivial answer, but its not always implemented. Some medical schools use board-exam like tests in their courses, but some are pass-fail. If you're in a pass-fail course its important to realize that you're preparing for the USMLE - and study that way.