There is a rule that I once heard: "Always be nice to people who serve you food." I think it goes for drinks too. Those whistles and finger snapping remind me of calling a dog, why do people do that?

As for tipping... I tip if a waiter deserves it and not all waiters do. If you have a smile on your face I will definitely leave a tip, even if you get my order wrong, but if you are acting like you hate me just for being there, be lucky I pay at all :D