Just out of curiosity is the format you will be playing back .wav or .aiff? Not that you can do much about it now but those two formats that have zero compression for future reference.
You should be fine with putting your laptop output to full volume or close.
The mixer you are using should have a peak meter, it should have a bar that should range from -infinity (or 50-60 on some boards) to zero db and then from 0 to up to another number depending on the board you are using. You can adjust the level of the input audio using a gain knob, don't use the slider beside the peak meter, it should stay at 0. The peak meter should also be colour coded, green-yellow-red. I generally aim for the loudest point of my song to be around the middle of the yellow. You want to leave some headroom between yellow and red, the red area is where clipping will occur, that will create distortion which is not good.
Don't shy away too much though, if you set the gain too low you won't have a strong enough signal and on some pa systems that can cause issues.
As for the room there is not much you can do, you are going to get a decent amount of reverb but assuming that it's filled with people it shouldn't be too bad. The hall you are in will probably have speakers set up already, speaker placement for live shows is more important than volume.
Rule of thumb for anything is get as loud of a signal into your mixer without clipping. A weak signal is bad, clipping is worse.
Hope this helps, if you need anything else just ask.
haha just think how that sounds. triple cork 1620. HAHAHA thats some video game shit right there.
kiwisdontbounce, April 7 2009