1. Find out what the "backline" situation is, if any. Sometimes on multiple band nights, several drummers are expected to play on one kit in order to minimize change over times, stage traffic, etc. etc.
If you are sharing a kit, make sure to follow the etiquette by bringing your own cymbals, pedals and snare. If its just your band and the headliner, just be sure to coordinate with their drummer WAY BEFORE gig night. That way, no surprises. Even then, be prepared to use your own kit....just be sure to find out if you are going to be setting up in front of the headliner's kit.
2. Be the first one to arrive...introduce yourself and make friends with the soundman first and foremost, especially if you are particular about your drum monitor mix. He will be your best ally and may help or hinder not only you, but your whole band. Also, it gives you a chance to tell him what to expect when the rest of your band arrives. Let him know what your set up is.....ex. we have a bass, two guitars, one vocalist ,and drums....the lead vocalist has his own wireless mike.
3. if you aren't already, be friendly and cool with the headlining band. I can't emphasize the importance of getting to know other bands and their fans....especially if you are the same genre, and expect to win new people over.
4. Make sure your singer gives the headliners a "shout out" and a thanks for having you-type thing. It will go a long way for good will.
5. Have fun!!!
btw, all these things were learned by trial and error after 300+ plus live shows in MD, PA,DC,and VA with hundreds of bands in the last 5 years! Hope it helps!!!