You ask a very general question, so it's difficult to provide many details. As a medical student, your income is likely small, but in many ways, you have to spend money to save money with the IRS. Again, in general, think of the IRS as being stuck in the 50's and it rewards people who live their life according to 50's-style values:
1. The IRS rewards 50's style households (spouse of primary breadwinner earns nothing/little,) in contrast, "modern" two-near-equal income families pay more than they would if theywere both single (though this "marriage penalty" has been mitigated big time by the Bush tax cuts, I believe.)
2. Children can be a big writeoff
3. Home ownership can result in big writeoffs
4. Charitable donations can be written off
5. Small business ownership (incl. Rental Properties) can result in BIG, BIG, BIG writeoff opportunities.
6. Live in a state that does not have a State Income Tax, because not only do you not have to pay the State Income Tax, but you can write off your sales tax, as well (though I think that this may be going away in 2010.)
This was a quick post, and I'm sure there are things that I forgot.