Get a double-bed size poly-cotton bedsheet, old or new, scrunch it up and stuff it inside the drum. That's it! Why this method in particular? Because you can adjust the damping to suit the room just by tilting the drum backwards or forwards and giving it a quick shake. You can have the sheet sitting mostly or all on the bottom of the shell, or touching the front and/or back head in any combination and to any degree you choose. In reality, of course, you don't worry about what's actually happening to the sheet inside the drum - you just tilt and wiggle it until it sounds right, then stop.
This works particularly well with smaller bass drums. 1. Tune both heads to their lowest viable pitch. 2. Add an extra turn or half turn to each tuner... 3. ...then de-tune *alternate* tension rods by half a turn or so - so for an eight-lug drum, for example, you would de-tune 2, 4, 6 and 8. This has the effect of disrupting the drum's fundamental pitch, so you don't hear much of the 'boom' - just a good, meaty thud. Add damping of your choice to finalise. Oddly enough, it's harder to do this accurately by simply de-tuning alternate rods upwards from step 1, which is why I don't suggest it.