General rule of thumb for me is to start the mini-me at 12 o clock, which I guess would correlate to about 30 db of gain or so, and usually work my way down. Gain however I find to be VERY microphone dependant, as well as venue dependant. If the house music pre-show is loud enough, which I find it generally is NOT, I try to get peaks at around -12 on the db meter. But really, and in actual uusage, just set them in the first three minutes and leave them alone...I usually don't leave them alone, but it is probably a god rule of thumb. Keep in mind with 16 bits it is really necesaary to run as hot as you can to maintain fidelity...not so much in 24 bits. I hope this helps, and if you have any further questions, feel free to ask!
Daryan