Timing
There are 24 frames per second. The more fluid you want your movement, the more inbetweens you'll create.
Ones:
If you create 24 drawings per second, that means you are animating in ones. This is the most fluid movement and is indicative of Disney style animation.
Twos:
12 drawings per second.
Threes:
8 drawings per second
Fours:
4 drawings per second
An advantage of the dance party assignment, is that most dances are a looping motions. Depending on the pace of your music and the style of dance your character makes, you may only need 1-2 seconds of drawings that you can then loop. Make sure that it loops cleanly. This is an opportunity to have a very fluid animation without completely overworking yourself.
Timing to the Beat
It is best to have your characters land a Visual Hit about 2 Frames before the audio beat. This is not a concrete rule. You may want your visual hit to be right on the beat, or even 4 frames ahead of the beat. It'll depend on your peice. However avoid visual hits that occur after the beat if you want it to have a good rhythmic flow.