If you're in a bar in the USA, sitting at the bar (not at a served table) is it customary to tip the bartender when paying for your drink (or leave a tip on the bar when you leave)?
You're supposed to, and if you don't, you can expect your next drink to be watered down or--if it's being prepared behind the scenes--it might even be spat in, so think twice before 'stiffing' a barman in the 'good ol' ' U.S.A.
