Setting up volume levels in a venue is very important. You may or may not know the saying but it is better to take away than to add. This goes with music production and sound engineering. As I mentioned before in previous tips be sure to keep all levels out of the red. This will lessen the intensity on everyone's ears and the speakers your working with. While DJ'ing in a club with a mixing board the first thing to setup is the gain.
Keep it the same as your mixer, below the clipping line, or center depending on the situation. Next you need to check your highs, mids, and lows through the main mixer. Set these to level with your input from your mixer. If there is too little of something remember to not raise the EQ, but instead lower what you have too much of. For instance if you have too little of bass consider lowering your highs and mids and now you will have more bass. Now if the venue your in doesn't have a mixer then that's okay you can set it all up on your mixer and it will be fine. You just have more responsibility on making sure your music stays monitored correctly.