One last note for now, leave things as close to how you found them as possible.
If you are fed separately, given a green room or a prep area, make sure you do your best to clean up after yourself. Even if there is wait staff assigned to you, make the offer to assist, and do as much work ahead of time for them.
A quick "Where do want us to bus this stuff when we are done?" to the person who brings the bandwiches goes a long way.
Minimize the amount of drinks and spill-ables on stage. Make sure at the end of the night, when you break everything down - it's as close to how you found it as possible.
A cell phone picture before setting up is always a help.
Caterers remember you. Hall managers and staff remember you -- look at them as your band-mates and co-workers for the evening. During breaks ask them casually how the crowd seems to be enjoying themselves, how liquored up they seem to be getting. If the caterer provided the food you had, make sure you compliment it and ask for a card.
Make sure you talk to the photographers -- exchange cards with them as well.
Keep in mind, this all has to be subtle and restrained. Do your job, you are there to entertian the crowd, don't interrupt others doing their job, but make sure you network -- it is a business after all.
Do you clean up after your gigs? What kind of networking have you done at gigs?