How much should you TIP at a restaurant with bad service?

ZERO!!! I haven ever worked in the food industry, and i think that if the service is bad, then too bad. I think that giving a bad tip is a great learning lesson for the employee. Then when they start getting good tips they can feel like they accomplished something.

I had a job where I lived on tips so I am a little biased on the issue. I always give 10% for bad service and 20%-30% for good service. Of couse I dealt blackjack for a living and I really didnt have any control over the outcome of what was going on (contrary to popular belief), so maybe Im wrong about the way I tip.

I would have not tipped at all, they didn't deserve it , and you friend in the food industry, is wrong, I pay for what i order and tip for the service, if one or more are bad managements hears about it, I am not stupid I have eyes and I can see if some one is trying to give good service, To day i was at a place and had a coffee and brand muffin, the bran muffin was burned, the lady said it wasn't the person who put them in the oven fault. I looked at her and said I have over 30 years in the food industry as a cook, so I guess I do not know what I am talking about. Those muffins should have been garbaged, not sold to customers, and then argued with when we dare complain.

i always tip on the way the service is... if we have a horrible server they get a horrible tip.. i have actually left a resturant without leaving a tip.. wrong drinks,cold food, dirty silverwear, and the waitress was extremely rude about everything... but i have also left a tip that was 50% of the bill.. and it wasnt that we were catered too it was anytime we need anything she was right there we didnt wait on anything she was smiling the whole time even tho i knew she was tired she was working a double shift.. i never tip on the way the food is prepared or the way it tastes simply because the server has nothing to do with that.. but i think you were right and your friend was wrong... always tip on service if its bad leave a bad tip maybe they will learn.. if its good leave a great tip they will appreciate it more

First of all, I resent tipping anyway. It seems to me that the business uses tipping to make the customers pay part of the servers' salaries. They pay poor wages and expect tips to make up the difference. That was not the reason the practice of tipping started. It was, as you say, to insure prompt service. While I resent the practice, I do tip anyway, because I know the salary is rotten and the work is hard. I used to be a waitress. For really poor service, I will leave a very small tip, 5% or less. Just enough for the server to know I didn't forget to tip, but demonstrate I was not satisfied with the service. If there is a comment section on the ticket or offered at check-out, I would fill that out, too. I choose not to pay for something I didn't receive!