"That was the worst service." -- ($0.01 {fixed} - 5%
Bad service -- 7% - 10%
okay service -- 15%
Good service -- 18% - 20%
"See you next week" -- 25% or more
Restaurant Server - YES
Drive Thru/ Fast food - NO
Cab/Uber - YES
Food delivery - YES
Any Grocery Store employee - NO
Bartender - YES, but it's only $1-3/drink
Valet (Car Parking Service) - YES