Smoke or drink as far from the dance floor as possible. It's easy to accidentally burn dancers in motion with a lit cigar or cigarette.
Spilled liquids turn a dance floor into a skating rink.
Dancing feet can get cut on broken bottles and glass. The floor is for dancing. Walk around the edge of the dance floor, rather than trying to thread your way through the dancers. When dancing, leave room on the edges for walkers. Good dancers are usually skilled at avoiding collisions with other dancers, but unnecessary obstacles are annoying and take up dancing space.