DJs should never control their own volume. They can't hear the sound hitting the audience because they're not in the audience! Your volume control (usually on a sound board) should be handled by someone in a position out in the audience.
But the DJ wants it loud! That's fine... aim a monitor speaker (which just plays back what he's playing) directly at his head from close range. Preferably two, one from each side. Now he gets to hear his sound nice and loud.
You can also place the speakers behind the DJ, so the DJ hears everything and gets deafened by his own noise.
Proper speaker position helps things sound better. Speakers (other than the subs) should be elevated above head height. Low speakers will bounce sound along the playa, scattering it to your neighbors... plus much of the noise is dampened by the bodies of the dancers before it hits ears. If your speakers are higher and aimed down, you can aim the sound at the center of your dance floor/party space and use much lower volume to get the same effect on the floor, while heavily reducing sound outside your dance floor.
When aiming sound, remember that speakers generally spread about 60 degrees horizontally and 40 degrees vertically in their peak sound area. For most purposes, you want the speakers at just above head height, generally on standard tripods. Bigger camps will want to go higher. None of this applies to subs, whose noise is so low it doesn't matter. Low pitch sounds scatter heavily, and aren't dampened much by people. Plus those things are heavy. Leave 'em on the ground.
Elevated speakers must be well secured. Speakers falling on people sucks. Please don't moop the blood of your attendees. It's rude. This is especially true if you stack your main speakers on your subs for height... strap that shit down. Subs vibrate, which can dance a speaker right off even without wind.
Aim the speakers through your own camp, not straight out into the playa (or at neighbors) where possible [Placement Note: EXCEPT if you’re a camp with frontage on 10:00 or 2:00 avenues. Those should face out to the open playa]. The nearest sleeping area to the front of your speakers should be your own sleeping area. If you can't sleep, that should tell you something. This is especially important for those "running all night ambient sound" camps with a pair of speakers on stands.
Dampen your sound. You can put solid padded material (such as plywood with egg crate foam on it) in position to bounce and dampen sound waves away from areas you don't want it to go. Your neighbors will love this.
If the music's playing, someone in camp who can operate the sound system should be there at all times. That person should be easily accessible for your neighbors/rangers who get called in because your neighbors are going insane. Be nice to your neighbors!