I always tip 20% in restaurants...if the service is above average...that way, if there's something a little "sucky" about it, I can drop it down to 15% (or 10% if it's tolerable)...
My first job, getting a paycheck, involved a sit-down dining establishment. I didn't work the tables, I was in the back doing everything except counting the money...the waitresses we're making $1.15/hour + tips...some of them did pretty darned good...others had the attitude that it was owed them. Those gals didn't last long...but the ones that made the dough worked their tails off...
Waiting on diners isn't an easy job...you're dealing with how many people with how many problems and each person is bringing their troubles and tribulations to a table you have to service...you're nothing but eye-candy and the best you hope for is that they don't "stiff you" on the check and you get some sort of reward for putting up with their table manners...if those exist anymore today...
And our waitresses worked the floor with 4" heels and frickin' short skirts...when they were back in the kitchen, it was like watching little kids the first time they were up on ice skates....

Walking on 4" stilettos on greasy floors was an art...and when one of the girls would break off a heel, it was like watching a NASCAR crash at the finish line...
Kuan...keep the servers in cash...skim back elsewhere if you have to...the girls
will remember you if you treat 'em nice after the service...