...most d.j.s will be reluctant to give away anything from their own bag-o-stylin', but since pretty much everything under the sun has been done and can be found out about one way or another:
1. Create your own bass kick - drop the highs and the mids on the deck you're cueing up, put the bass up a little higher than usual. Leave the stylus on the record, but don't start the platter. Cut-n-phase as you please while tapping your finger on the body of the turntable near the counterbalance to create a nice solid THUMP - don't overuse. Claude Young/Dave Clarke style ammo - simple and very effective. Can also be used for mids.
2. Tone generator - takes practice if you want it to sound polished, otherwise you just end up with an annoying, sustained buzz. Turn down the bass on the unused channel, turn the highs up to level and the mids up a bit higher than usual. Start the platter, but instead of placing the stylus on the record, take the headshell and rub it against the nubs that indicate the pitch. The resonance running up the tonearm will produce a hum that you can control by how much pressure you apply, and by adjusting the pitch control as you go. Works well with three decks.
ta-da
i.