The dancers move counter clockwise (from above) around the floor.
When things go wrong on the dance floor always apologize. Generally it does not matter who is at fault.
If you are moving more slowly than other dancers keep to the center of the floor.
If you are engaged in conversation move off the dance floor.
To cross the room either dance across the floor or walk around the perimeter.
Carry food and beverages around the perimeter. Wipe up your own spills.
While dancing, do not give dance tips unless asked. If asked, just give tips about what you were asked about. When engaged in giving a lengthy tip, or if you stop dancing to discuss it, move off the dance floor. And, above all, don't give that person tips again until they ask you again.
The traditional rule about declining dances was that you could politely turn down a request to dance only by saying something like "No, thank you. I'm sitting this one out." or "I'd be happy to dance with you later. I just need to rest now.", and that if you turn down a request to dance, to be polite, it was considered important that you not dance at all during the dance in question. Many dance groups today have abandoned this rule, and explicitly say that it's always ok to decline a dance with a simple "no, thank you", and no reason need be given.
Don't just dance with your favorite dancers. It's called "social" dancing for a reason.
It is always up to the follow, not the lead, to set the distance between the partners. However, if the lead feels like he is being held too closely for comfort or safety, they might say something like "If you move away a little bit, I'll be able to lead you more safely." If either partner is not being allowed to set what they feel is a comfortable and safe distance, they should feel free to say that they need to sit down to rest, or something else equally polite.