Get expectations set firmly in stone before the evening has a chance to begin. If this does not happen, things only go down hill and someone ends up mad, disappointed and even hurt or in trouble. I strongly recommend post-prom. It gives the students a chance to make a little money back. There are fun games and lots of prizes.
Prizes vary from gift certificates to new computers, and all of it is free.
This event is what I look forward to. Sure, prom is fun, but post-prom is awfully hard to top. It is also a way to stay out of trouble. So, in a condensed version, that is the wisdom I have obtained from proms so far that I can pass on to others. Again, just make sure you remember to plan ahead.