My experience, as learned the hard way, and not necessarily correct in every region...

Germany: tip is the leftover change from the bill. If the bill is 18.95 and you pay 20, then it's the .05.

France: Tip is included in the bill usually. I made someone very happy there my first night...

Haircuts: I always tip, but I've been going to the same guy for six years now. He treats me well and occasionally schedules me in when the shop's closed. I also get a bottle of his special home-brew booze at Christmas time...

Also- ask how the tips are split. Some places will have whoever collects it, gets it, some spit the sitting bit into sections with teams on the areas and they split it, other places spilt everything even at the end of the night, there are eeevil places that keep tips for the company (apparently) and there is my work- the tips are saved up for around half a year and split to everyone except for management: including chefs and recetioists and lifeguards etc.

Just incase you think the waitress served you good only to discover that they get not a single penny from your tip.