15-20% tip is costumary for any kind of service, as far as I know? I don't worry about if a meal is buffet or not. I always tip that much for a restaurant, cab, haircut, pedicure--etc.
Even if the service is less than stellar, I tend to tip that.
I have never even heard of a 5% tip for anything! 10% is sort of old fashioned--and 15-20 is typical. I always tend to give 20% just because it is easier for me to figure out in my head!
I think
Disneyland uses the 18% gratuity because it is right in the middle of the customary "15-20%" tip that most people ordinarily give.
This is from money magazine--tip guidelines:
General rule: 10% usually means you are very unhappy, 15% usually means all was ok, 20% for excellent, and 25% for outstanding.
Restaurants with table service: Tip 15% of the bill, based on the quality of service. If you receive exceptional service, 15-25% is customary. In major cities of the U.S. however, 20% is considered to be a "good tip".
For bad or unacceptable service it is customary to tip as low as 10%. If service is bad enough to deserve only 10%, it is a good idea to let the manager know.
Buffet Service:
For buffet restaurants, a tip of 15% to 20% of the bill is still recommended because the servers often work harder than in normal restaurants. They may not take orders or bring out food, but they do work hard keeping your table clean of the empty plates after multiple trips to the buffet line. In addition to this, they often help to keep the buffet line stocked and clean, and they make coffee, brew tea, etc. Remember that the minimum tip for any server should be $1 per person. Do not leave only 75 cents for a $5.00 buffet!
I think that the reason that Disneyland has added in the gratuity to the bill at Goofy's and other buffets is because some people feel like once they have paid for the buffet they shouldn't have to pay more for the tip.
