Etiquette wise, i know it used to be, always, always clean it when you leave. And don't harm or damage it.
If you take a beer or two, replenish next trip. Same with joints or roaches. A lot of people just left the roaches in there for others and it was always expected to leave one in return when you could.
I had some friends go up there in the summer and grab all the roaches when the town was dry, then they'd roll some pinners and just leave them there once town was supplied again.