Ugh! I HATED working in the bar, because people would shake their glasses or bang them on tables to try to get my attention.
I completely ignored one guy, until he got super pissed and finally ASKED for a refill.
I smiled sweetly, told him that that was all he had needed to do; ask, and STILL got a fifteen dollar tip on a twenty dollar tab.
People who shake glasses/snap fingers/clink ice at waitresses should choke on their drinks. =]