4. The lights get lowered and people start cheering, even though the house music is still playing. (*hint* -- look for the guy waving a flashlight, then you can scream).
3. Somebody yells "Freebird" or some obscure B-side.
2. Some near-do-well will take flash photographs with their point and shoot, thus blinding the performers.
1. The opening act says, "Hi, we're such and such. We come from Brooklyn. We have two more songs for you. We have merch in the back."