About the tip for less-than-full-service:
I generally leave something at the Chinese buffet places I go to. Somebody keeps the water glass filled, brings tea, busses the table, etc...
Not a strict percentage, but a few dollars. I'm sure the help can use it, and I can afford it , for now.
I draw the line at McDonalds-type places where they bring the food to the table if there is a delay....
Most of those spots, fellow customers might get to the tip before the busboy.....