in addition to heads and tuning (both very important), make sure to check your bearing edges and whether the shell is in round.
set the drum, without the heads/hoops on, on a flat surface like a table. if you can wobble the drum, your edges are fucked up or the shell is out of round. both of these can make your drum sound like shit (but not necessarily - i have a set of ludwigs that have messy edges from being abused by the previous owner, and they sound like heaven and hell).
also make sure that you're hitting the drum in the center of the head and HARD. hitting it with a limp wrist will emphasize the stray cat frequencies.
you might also want to try recording them, turn up the overheads a bit, and see how it sounds when recorded. they may not "sound like shit" when you're listening through a bunch of microphones.