Foolish assumptions: (I assume you do these things right)
- You're putting a separate microphone on each drum, within 6 inches of the drum head.
This including the Kick (bass) drum, the snare drum, and any toms if you want to give them punch. Of course you can do this trick on just the kick and snare, so if you're using a 4-track, I recommend close-miking the kick and snare, then using a pair of stereo overheads for the rest of the kit.
- You're recording each mic onto it's own track in your DAW (protools/cubase/live/etc).
If the drums you want to 'enhance' aren't separated in the computer, there isn't much you'll be able to do with them. Again, it's always better to have EVERY mic on it's own track, but if you're working with limited resources, you can use an outboard mixer to run the overheads, and tom mics in as a stereo pair, and the kick and snare seperately.
- You're recording in STEREO.
You'd be surprised what a difference it makes panning the toms 50% either way. Also, a Stereo Pair is a must for overheads.
Now for the good stuff...
STEP 1: Add a compressor as an insert on the drum track in question (this is how you usually add effects, so if you're not sure just add a compressor plug-in to the track and you're probably doing it right). For this example I'll be using the Waves Renaissance Compressor...
STEP 2: Set the ratio to 5:1. You can experiment with this, but it needs to be pretty high for the effect to be noticeable.
STEP 3: Set the attack to 35 ms for most drums (snare, toms, etc), and 45 - 65 ms for bass heavy ones (like the kick or a deep floor tom).
This is how you control how much of the POP! gets through the compressor. You want just the initial crack of the drum to get through so you can boost that part with out the ring, and bleed of the other drums getting though. The longer the attack (high number) the more sound gets through before the compressor kicks in. This is especially important for bassy drums because if you set the attack time too low, it'll actually squash the low frequencies out of the drum.
Set the release for 85 ms. (don't change this for any reason, unless you have a problem with the compressor carrying over onto the next drum hit and squashing it. In that case, lower the number as necessary.)
Note: you won't hear any difference one way or another until you do step 4, so just use my recommended values for attack/release for now.
STEP 4: Set the threshold so that (with a 5:1 ratio) average drum hits are compressed 5 - 10 db. The lower the threshold, the more noticeable the extra POP! will be.
Make sure the compressor returns all the way (or almost all of the way) back to 0 dB of compression before the next drum hit though, or else everything is gonna sound all F'd. For fast drum parts, this is when you may need to lower the release time.
Experiment with putting the threshold all the way down (around -45dB) so you can hear what's going on with your compressor.
STEP 5: Finally, adjust the gain until your drum is as loud as it needs to be.
STEP 6 (optional): In many cases, it's preferable to run all the drums through a group bus, and apply a limiter at this stage. I usually do this for and rock music I work on. The techniques for grouping tracks into a group channel with it's own inserts is different in each DAW program, so I won't get into it now, but a Google search will do you a world of good.
The famous Waves L1-limiter on the Drums output bus: