I guess I tip well, restaurants 20% + IF THE SERVICE WAS GOOD. If the service is terrible, I have no qualms about leaving little or nothing (but that's rare).
I was a bellboy in college and a parking valet once for awhile after being laid-off, so I know how it is to have a tip job. Man, I busted my ass and it pissed me off to no end to get either a shitty tip or no tip. When you're making less than minimum wage (legal if it's a tip job - maybe varies state to state, I don't know) to start with, the tips are what make you or break you.
At my bellboy job in college (Univ. of Hawaii - Go Warriors!), the worst tippers were Canadians and Australians. Getting a tip from them was an event as frequent as Haley's Comet. The running joke was "What's the difference between a canoe and an Australian/Canadian?" Answer = Canoes tip. So I usually tip bellmen well, because I've been there, but I must say that my last couple of stays in Vegas it took FOREVER to get my bags, like almost an hour! Unacceptable. If it happens again I'm not going to tip much.
My valet job was at the Esplenade in Phoenix. There's a Morton's there so we had a lot of their customers. Average tip was $3 I'd say. What blew my mind was how sometimes obviously well-off people would arrive in expensive cars, say a Mercedes, I'd be totally polite to them and quickly retrieve their car when they came out, and they'd either tip me nothing or a buck, or worst of all - loose change! Just insulting.....But there were cool people as well. A lot of the Phoenix Suns players would park with us and they'd usually tip $20. Cliff Robinson was way cool. Tony Delk, Marbury, and Penny Hardaway - good tippers. Absolute worst = Vinnie Del Negro. Cheapest SOB "celebrity" I ever met. He was notorious for not only not wanting to tip, but not paying the base parking fee of $3! Haven't seen him playing recently. Good, I hope the bastard has his entire savings in Enron.
That's another thing: when you have your car valet parked and you see there's a charge up-front, say $3, DO NOT assume that the valets are getting that money! They get a tiny percentage, say 50 cents of that $3! Most of it goes to the owner. The valet guys are earning 2 bucks an hour + tips.
Hotel maids I have a sweet spot for. Those ladies earn their keep. Imagine all the disgusting stuff they see and have to clean every day (not my room of course!). I talked to one at the Rio in Vegas, and she told me horror stories that made me sick. Amazing how people can turn into animals when they're not staying at home...