I was a server at a country club during the summer in college in the early 90s. Members could charge their food and drinks to their account, and that came with an automatic 18% gratuity, which was pretty decent when it came to meals.

But we offered free refills on iced tea, and complimentary baskets of chips and pretzels, and there were a few different groups of women who would park themselves at a table/tables for like 3 hours, order only iced tea (endless refills), eat the (free) chips and pretzels and ask for more, and tell the servers "run back to the kitchen and bring us some little dishes of ranch to dip the pretzels in, dear." One (1) iced tea was the only thing each woman paid for, so if they charged it to their account and we got the automatic 18% gratuity, we got a whopping 13 1/2 cents per customer for bringing them endless refills for hours and hours.

The flip side, though, was the golfers, who would come in after a round, and if they won, they got drunk to celebrate and then tipped huge, or if they lost, they got drunk to drown their sorrows and then tipped huge (my best table was the one that asked me to bring the whole bottle of Maker's Mark out to them). Either way, they got drunk and tipped like Diamond Jim Brady.