Well, you could remove all music, and alcohol, and it would be safe to dance then....

Or more sensibly, you try and make sure the floor is a reasonable size, and not too slippery. Here in Edinburgh, we use slipstop alot, its a rosin based powder which gives you more grip, although that is more common when we have a decent proportion of us in soft soled pumps/ghillies, which need all the grip you can get.

As regards to ASBO type dancers, just refuse to dance with them. Or, if yoy're feeling patient , you dance with them, and try and calm them down, or at least get them to listen to the music, and be more aware of the space around them, ie teach them. Even good dancers can have accidents

You only seperate dancers of differing abilities for the purposes of teaching, not for social dancing.

I'm demonstration convener for a Scottish country dance society, and so frequently end up running the dancing at ceilidhs with all levels of ability present, and so know more about this than I want to.....