While there may be some correlation between MCAT scores and USMLE step 1 scores, I wouldn't approach them the same way at all. The MCAT is a prospective tests which mostly tests your understanding of broad concepts and your reasoning ability. I don't know about you, but I really didn't study much for the MCAT -- I mostly just did a practice test the week or two before, then spent a little time reviewing. I haven't taken step 1 yet, but from the practice test I took and what I've heard from others who have taken it, it really tests your knowledge and is pretty detail oriented rather than being something you can figure out from basic principles. Of course the first two years of med school should have started to prepare your for the boards, but you should plan on spending a significant amount of time reviewing (most students at my school take about 4 weeks, studying 8-10 hours a day). Depending on your school, some important topics may not have been covered in detail in your classes.
That said, they are both standardized tests. If you do well with those, that's one thing you've got going for you, but don't expect it to carry you through. If you don't do well on standardized tests, you are going to have to make sure you know the strategy for narrowing down choices, budgeting time, etc. You'll find lots more about specific strategies in the USMLE Step 1 area.
