Normally, I mike everything once. That's snare, 3 toms, kick, 2 overheads. However, I'm beginning to add another mic to the bottom of the snare, inside the kick (when I get the money to get a beta 91) (as well as an akg d112 outside), and on top of the hihat and ride. This will total to 11 mics. When I can get hold of a decent bass amp, I'm going to reverse the polarity and use it to pickup the low end of the kick by placing it in front of it and recording through it (search the forums for this technique).
Again, it's all about mic placement. You can get decent drum sounds just from overheads. ...Read up on mic placement and phasing issues, because if you're going to use two mics on the same drum (e.g. one on top and bottom of snare, pointing semi-at eachother), you're going to run into phasing issues which will really affect your sound, so search the forums for phasing preventions.