I usually tip 15%-20% in a restaurant where the wait person takes my order, brings food, freshens drinks, etc. But at buffet, or a restaurant where menu selection and buffet is offered, how much should one tip the wait staff that only comes by to take your drink order and say, “Help yourself to the buffet”.
Similaryly, how much to tip in a dim sum restaurant – a reverse buffet where the food moves while the diner stays put and still not being “served” in the usual sense by a wait person.
In buffets I tip 10 percent.
I’ll usually leave a dollar or some change on the table, if anything. It’s not that much of a service to clear plates away, and at some places, they don’t even clear until after you leave.
If there’s an option to tip the chef (like at a sushi buffet I frequent), I’ll drop a tip in his tip jar. Usually around 10-15%.
I don’t tip at a restaurant unless they bring me a menu, take my order, bring me drink refills, bring me food, and bring me the bill, all without my having to get up. I generally tip 20-25 percent, but if any of those steps are skipped or not carried out in a timely fashion I tip less.
I don’t tip at any restaurant where I have to serve myself.
I don’t tip at any restaurant where they have a large menu posted and I have to wait in line.
So its possible that I’d tip at a buffet restaurant, but they better bring me my drink refills and a waitress better be available to provide service.
At a buffet, I usually leave a dollar for every person who ate. I guess that’s close to 15%.
To clarify, I never leave less than a buck, so it does go over 10 percent frequently.
A dollar per person eating, usually.
The only exceptions are if the wait provides service above and beyond the call of duty*, or it’s a holiday.
*Like actually being able to keep up with my drink refills 
<Reservoir Dogs>
Mr. Pink: I don’t tip because society says I have to. Alright, I tip when somebody really deserves a tip. If they put forth an effort, I’ll give them something extra. But I mean, this tipping automatically, that’s for the birds. As far as I’m concerned they’re just doing their job.
Mr. Blue: Hey, this girl was nice.
Mr. Pink: She was okay. But she wasn’t anything special.
Mr. Blue: What special? Take you in the back and suck your dick?
Nice Guy Eddie: I’d go over twelve percent for that.
</RD>
Depends on the buffet and how much they do.
When I go to the Indian buffet, they bring me naan, water and generally are very sociable. One of the places brings me complimentary tea on occasion. I usually tip $1 or $1.50 on a $7 buffet.
Most buffets I will tip $1, sometimes nothing if it is self-serve entirely (I pull drinks, get food, pay at register, they just bus the table).