Don’t Play the Whole Song
The worst is when a DJ plays the whole song with a small three second silence before the next song starts.
I was at an event with my wife and there was dancing. The DJ played his music this way, and it sapped all the energy from the dance floor.
Even if a song is crushing it, that doesn’t mean to keep playing the full song. Move onto the next one while the energy is up. Dancers get a high every time they hear a new song coming on, wanting to hear the chorus that they love. The problem is most people aren’t going to know the second and third verses; at these times the dancers will get bored and start thinking about what else they could be doing, like going back to their table to have some water or another cookie. Playing the whole song and having silence between songs is even worse and utterly terrible at keeping attention on dancing.
I quick mix which means I focus on playing around 30 seconds to two minutes of a song (and play the best parts). Make sure your DJ knows how to mix. Not only that, they should have enough music prepared so they are excited to quick mix all night long.