hmmmm lets see what I can tell you.
1. While studying the textbooks, do pay special attention to clinical applications of important points. For example, if you are studying glycolysis in biochem, do pay great attention to enzyme deficiencies.
2. In pathology, try to understand the slides, I didn't do that and then had to start from the scratch on that one.
3. Do your microbiology very well. Not sure about others but for me its one of the toughest subjects as most of it has to be memorized.
4. ELECTIVES!!! You are still an undergrad so you should avail this opportunity while you can. Electives are hands on clinical experience which is what most of the programs are asking for nowadays, or atleast prefer. Hands on clinical experience after graduation i.e externship is not easy to get.
5. Don't let others discourage you. Some will say you should concentrate on your curriculum and not worry about USMLE while others will say its hard to get a residency so why go for steps? But don't listen to anyone discouraging and do your thing.
Again, Best of luck!!!