Don't do dance or costume contests. Social dancing isn't about competition, and neither is dressing well--and these and all other bits of extraneous business (raffles, door prizes, visits from Emperor Franz Josef etc.) can throw off your timing if you aren't very careful. Contests often also lead to bad feelings on the part of those who weren't selected.

Don't do dance demonstrations that aren't tied to actual instruction. These cut into the time your paying customers have to dance, and can also intimidate novices by saying: "This is what REAL dancers look like you hopeless slob".

Provide a variety of dances--not just waltzes and polkas. Quadrilles and other set dances break up the program and are also an excellent entry point for novice dancers. An occasional Mazurka or Schottishe is also a nice break, but don't do many of them, as few dancers know them.

Assign a Master or Mistress of Ceremonies who has a lot of "stage presence" and who can also keep the band on schedule. Prussian efficiency is essential if you are using a dance card. Placing a dance on a card is something of a contract, and it is VERY bad form to have to cancel a dance that people have already made engagements for. If you haven't figured out the timing down to the last minute, then under schedule and keep a few "bonus dances" in reserve.

This Master of Ceremonies must frequently and forcefully remind people about the "Line of Direction", and remind them that dancers moving at high speed should be on the outside and the dancers who aren't moving at high speed, either because they are inexperienced, they are modern box-steppers, or they just want to show off; should move to the center of the floor.

And finally, "Floor Managers" are essential if you are having set dances in a dance with over 100 people. You need people who know what the set dances should look like to coordinate with the dance caller on the stage to move people around on the floor to get them into the right places. It is too much to ask of one person, on a stage, to try to sort thing out by shouting "Hey, you in the pink dress--no the other pink dress--move to your right...".