Good Choice

I believe that coming up with songs appropriate for each dance form is up to the DJ's experience as a dancer.  "This sounds like a cha cha to me."  His/her intuitive hunches are what make every DJ different.  There are no correct answers, and each DJ will have his/her unique sense of whether their tune choice works well for that dance, or not.  Then the dancers each have their unique sense of whether their dance choice works well for that tune, or not.  Everyone is following their hunches, but a part of this process is also objective:

After we come up with an intuitive guess, then we can easily check the tempo, to see if it's within 10% of the sweet spot tempo (below).

We easily tell whether it has a driving high energy or if it's gentle/lyrical, to match to the tempo being above or below the sweet spot.

But coming up with that first intuitive guess is what makes each DJ unique.  My tips don't want to influence that individuality.  The suggestions on this page are just to help increase the percentage of tunes that make the dancers happy.

Not to do

Don't choose tunes primarily because of the lyrics, title or clever name of the band.  Most dancers don't listen to the lyrics when they dance.  Dancing is a very non-verbal activity, so choosing a tune primarily because of its lyrics has almost zero value to the dancers.  Besides, dancers come to have fun dancing, not to admire how well the DJ strings together a series of songs on a special topic. 

Don't choose a tune primarily because it's unusual or weird, at the expense of it being an effective dance.  Don't get me wrong — weird music can be great when it's danceable, but the first priority is meeting the above requirements, motivating the dancers and having tempos perfect for their energy level.  If these are met then yes, obscure is fine, and weird is fun.

So the key word here is "primarily."  If tunes have a special theme and are wonderfully compelling to dance to, then there's no problem.  But too often a DJ's quest for special themes or lyrics leads them to dig up tunes with undanceable tempos and hard-to-hear beats.

All suggestions have exceptions.  Occasionally (rarely) the words will be important, like song lyrics about a father and his daughter, played for the father-daughter dance at a wedding.  But in general, lyrics aren't the reason to choose your dance music.

Monitoring volume level

The volume level of your music presents a pair of tricky problems.  (1) With only a few high-tech exceptions, the volume level can be too loud directly in front of the speakers but too quiet at points farthest from the speakers ("I can't hear the beat").  (2) And as your song alternates between its loud and quiet sections, ambient party noise usually drowns out the quieter passages, then blasts your dancers painfully during the loudest parts.  This doesn't happen in the quiet of a concert hall or at home... it's a dance party dilemma.

Because of these two problems, there's a very narrow range of acceptable volume.  Any louder and it's hurting the ears of those closest to the speakers; any quieter and it's inaudible for other dancers.  Then as most tunes decrescendo and crescendo, your music quickly goes from inaudible to painful, because of the very narrow range of acceptable volume.

Your responsibility as a DJ is to constantly monitor the volume level, lowering it during the loudest parts and raising the volume during the quiet passages.  A concert purist might complain that acoustic music doesn't do that, but here music is functional and inspirational to dancers, and must be modulated to best support the dancers.

This responsibility as a DJ might involve some self-sacrifice — foregoing the pleasure of dancing yourself.  I'll often be at a DJ'd dance and be surprised that the DJ let the music suddenly get painfully loud, or ineffectively quiet.  Sure enough, each time the DJ is out having fun on the dance floor, away from the volume control.  If you want to dance, ask someone to take over the volume control for you.  My solution, if it's one I know I'll want to dance, is to record a version in which I've adjusted the volume peaks and valleys ahead of time.

You already know this next point, but just to be thorough, the DJ often sits in an acoustic shadow behind the speakers, so the music doesn't sound as loud to the DJ as it does to the dancers.  During your first song of the night, go out onto the dance floor to make sure the sound isn't blasting those closest to the speakers, and not too quiet for those at the far end of the hall.  Check again when the floor becomes more crowded, since bodies absorb sound and change the acoustics of the dance floor.