As the room fills during the night, all those bodies absorb more of the volume and you have to compensate. Alternatively, as the crowd thins down, you have to lower the volume to compensate. Other factors can affect volume as well such as the temperature in the room.

Finally, when you are doing a seven or eight hour shift, your ears will get weaker as the night wears on and you'll tend to compensate by bringing the volume up.

Try and get a few different people's opinions at different points around the room. During your shift, make a habit of getting out of the booth and listening to the system from various points in the room. If you use a wireless mic, take it with you so you can hear how your voice sounds as well.

Keep an eye on the booths at the edge of the room or wherever dancers tend to take the guests to do table dances. Do they have to shout to carry on a conversation? If so, adjust your volume accordingly.

Some club's sound systems have different zones setup so you can vary the volume for individual sections of the room. If your club allows you to adjust these, do so but mark the original settings before you make changes so you can change things back at the end of the night.

If the zone volume controls aren't properly labeled, don't adjust these individual controls during the shift. This isn't the time for trial and error and you could end up damaging the system. You can check these settings after-hours at a low volume and label them for next time.