None of the poll results really fit my approach (the "your standards" part makes it complicated - some people's standards are simply unreasonable and absurd), I think, which is this:
Unfortunately, in the U.S., the tipping system is what the waitstaff rely on just to get up to normal minimum wage. If it's a slow night a waiter/waitress can make less than minimum wage (as the standard minimum doesn't apply to tipped waitstaff). I don't think that's right.
Thus, if the service is reasonable and at all acceptable - and I'm NOT that hard to please - then I'll tip at least the 15%, probably more like 20%. If it's really good to excellent, then I'll probably go from 20-25% If they're asking me every 10 seconds how my food is and if I need someone to talk to about life's problems, then that's a bit much, and they're starting to annoy me and not gonna get a bigger tip.
But if the waitperson is downright rude, snotty, snappy, etc., or quasi-hostile, then, depending on how bad it was, I might just skip the tip.
Incompetence or bungling is a harder call. Everyone has bad days or even really bad days. If my cold drink gets dumped in my lap, but I get a sincere apology, I will probably still tip. Hot drinks are a different matter, but hey, if I don't lose my ability to reproduce (or, more importantly, FUCK), then the tip is still possible...
But if the person just seems really incompetent and inept and not cut out for that line of work at all, then giving little or no tip might encourage them to consider other work...
But I'm saying it would have to be quite bad.
After all, if I'm paying for part of this person's salary, and not just for the cost of the meal plus the owner's expenses and profit, then why shouldn't I have some influence on personnel matters?
So, I find that I give a tip about 97-98% of the time, and I try to be generous. Excellent service brings out my generosity. Adequate service will get me to do my duty and give 15%