Just stop the music, say, "Woah, woah, woah!" and state your concerns. Spilled drinks are a real hazard, potentially twisting someone's knee leading to a lifetime of pain.
Fortunately, nobody is enough of a jerk to be consciously inconsiderate. And if they are, you want to know who they are.
There should definitely be a no-drink policy on the floor.
As for kicks and elbows, a class on space etiquette helps. Non-sequitur music selection helps.
Bad dancing doesn't deserve good music.
Calming a crazy floor
Moderators: Mr Awesomer, JesseMiner, CafeSavoy