Monday nights suck in the restaurant and bar business. Monday nights are not a night that people tend to go out. If the restaurant is getting less business from other customers it is not because our group is there. It is the same reason that they are getting less money from us these days. The economy sucks. Yes, I'm also one of the unemployed many out there. Customers are not walking away because of the group. If I was a family looking for a meal and was staying at the hotel would I walk away because people are playing board games? Of course not. As a parent, I'd much rather see that than a bar full of drunks. If I don't see a table available, do I ever walk away from a restaurant? Never. I walk up and ask for a table and only if the host(ess) says there is a long wait do I ever consider a decision to go elsewhere.
Any restaurant that turns down a large group of people, no matter how much they spend, on a Monday night would be crazy, expecially these days.
Having said that , all of the other things that people have mentioned are always a good thing to do on the game night or otherwise. Tip your bartender/server well, whether you order a mixed drink, cola, or water. Consider ordering appetizers or a meal if it is in your budget, since you do have to eat anyway. Clean up after yourself and be curteous of others around you.
It's all really just common sense after all.
All my best,