The going tipping % is now %18 here in the USA. (Years ago it was %15.)

The only one you don't tip is the owner of the establishment. So if the owner does your hair, or the owner of the restaurant is your waiter, you don't tip.

For luggage handling when traveling, everyone who touches your bag gets a dollar. If the cabbie puts your bag into the trunk, he gets a dollar (but only once for in/out) and thus along the trip. It's $1 per bag, by the way.

The thinking is, if you can't afford to tip (and by that it is meant to tip the proper amounts) then you shouldn't be going there (restaurant, salon, travel.) You are cheating the worker of wages if you don't tip properly.

Good topic, btw.