Ok, here are my guidelines: If the waitress is ok (polite, refills drinks in a timely manner when asked, clears table efficiently, etc) I go with the standard 15%. If she rocks - as in is not only polite, but goes above and beyond the waitressing call of duty such as anticipating drink refills, plate clearing, has a sparkling personality, I'll bump up accordingly.
Ok, if the waitstaff isn't good, it depends. If they cause me to have to leave less than 15%, I'll write them a note on the bill to tell them. Because, honestly, if you leave less than 15%, or stiff them, the waitstaff is going to assume the problem is YOU and you are just a crappy tipper, not that it is anything they've done. So on their copy of the receipt or bill, i'll jot a note and just say something like "My food was good, but the waitstaff didn't offer refills/serve in a timely manner/ wasn't polite - whatever"
If there is a serious problem, such as dinner came out before appetizers, drinks NEVER got refilled, it takes 45 minutes for them to clear plates and give you a dessert menu, let alone deliver a bill, etc, then it is manager time. there is absolutely no excuse for that.
On bad tippers: I don't think that because someone is a bad tipper, it means they are a bad person. My grampa was the WORST tipper ever, because he didn't think he should have to tip, but didn't understand that most waitresses only make $2 or less an hour without their tips and have no benefits. But he was the sweetest man.
I don't think people who have never waited tables really understand how hard it is. For me, it was much harder than being a planner (which is why I went to college). And my brother and sister, who also waited tables through college agree that the job will make you hate humankind because it is surprising how many people treat their servers like crap. it is rough physically and i have no idea how those 40 and 50 year old ladies do it.
Ok, ONE LAST THING and i'm done - there are things that are not your waitperson's fault, such as food taking a long time to come out, or even food being cold. the guys in the kitchen are in control of that (Unless everyone at the table has cold food, then it is your waitress's fault that she let everything sit). BUT your waitperson SHOULD let you know if the kitchen is overloaded or slow and apologize for it, so you're not sitting there wondering what the hell is going on - they're only making a sandwich and a burger for christ's sake. so keep that in mind. OH, and if your waitress is really overloaded with tables, then she should tell you and apologize if she isn't getting to you as quickly as you think she should.
sorry so long, but just wanted you to understand what's going on on the other side of the table. does that help E.G.?