How should I tip if the food is good but the service from the waiter/waitress is terrible in the USA?

cdkMoose is correct in that the quality of the food should not influence your tip. However, your question appears to operate on a bit of a false premise, and I think it should also be said that leaving a small tip for poor service should be done only in exceptional circumstances.

By exceptional circumstances, I mean active hostilty or extreme rudeness on the part of the waiter. In a case where the waiter is simply inattentive, you should still leave a full tip. Here's why:

• At many restaurants and especially during peak hours, waiters are severely overworked, and often cannot be as attentive as they might like.
• Wait staff at most restaurants in the US are paid almost completely out of tips. Getting a tip isn't a nice little bonus for good service, it's their livelihood.
• Few other professions demand such constant attentiveness with the possibility of immediate financial penalty for a single failure. If I'm having a slow day at work, my boss might reprimand me, but can't arbitrarily cut my next paycheck.
• Tipping culture is strongly ingrained in the US, and many will see leaving a small tip as extremely rude, even if service was suboptimal.

If you want to tip based on quality of service, I would suggest adopting the opposite mentality to the one espoused in your question; rather than punishing poor service, reward good service. For instance, plan always to tip 20% as a fixed 'service fee', but occasionally leave an additional 5-10% 'voluntary gratuity' for exceptional service.

I like to tip them the smallest value coin I have; that way they knew I didn't forget a tip. Then I talk to the manager or email feedback.

In many locations, tips are not only for the waitstaff, but are actually shared with the busboys, the bartender, and sometimes other members of the staff - usually not the cooks, but even occasionally then.

They're also a significant fraction of their wages, most waiters earning a few dollars an hour "plus tips" rather than a full, normal wage. When I worked in college at a local breakfast/diner place, low prices but high table turn, I usually pulled $10-$15 an hour in tips, and $3.15 an hour in wages (IL minimum wage at the time), for example, and gave 25% of that to the bartender and the busboys (15% and 10% if I recall).

Tipping zero or near-zero, especially if you're obviously not American, will accomplish nothing other than make them think you're a foreigner with no idea of our customs.

Instead, tip at the low end of your comfort zone - for me that's dead minimum 10%, most of the time 20% with average to good service - and leave a comment with the waiter or the manager, depending on what the problem was, if it was significant enough to justify doing so. If the waiter was simply inattentive, letting him know may be actually helpful to him in the future. If the waiter was rude or otherwise you aren't comfortable talking to him, letting the manager know is helpful; be aware that if you do it in person prior to paying, it sends a signal you expect some compensation, so often doing it after you've paid is better.

As a former waiter myself, I definitely would've appreciated being let know if I wasn't sufficiently attentive to a table - and most of the time I probably knew already. I was fairly good at my job, usually receiving among the highest percentage in tips of the restaurants I worked at (after the first one), but I still had tables I made mistakes at, days I wasn't as on top of things, or otherwise had issues. A quick:

Hey, thanks for serving me today. Don't worry about the iced tea I asked for.

is a pretty non-confrontational way of reminding the waiter he didn't do something you asked for.

The quality of the food is irrelevant to the tip. The cook gets payed a full wage and does not receive any of the tip. Therefore your only concern when deciding how much to tip should be on the service provided by the waiter or waitress. DO NOT reward the service staff for the work of the kitchen.

Personally, if I get bad service then I tip about half of the average; so about 7.5%. If I get good service, then I tip over the average (22.5%).

My wife's entire professional career has involved some form of tipping, so she often tips up to 50% and believe me this has not gone unnoticed. We would often have people recognize us when we enter a place that we frequent regularly, and get amazing service because they know a large tip is coming.

I've never received such poor service that the waitperson did not deserve a tip for their time. Most cases where the server did the worst job, they were obviously in, or just out of, training and still slightly overwhelmed.

I typically use 15% as a starting point. If it was on the extreme end of bad, I'll play fast and loose, maybe round to the nearest $1 and short them down to 14% or so. When I worked in a restaurant (15 years ago), the hourly wage was $2.13 an hour (or thereabouts... within $.10). Unless they are outright hostile to me (which has never happened), they deserve their 15%.

This is in the US.

Tim Urban's wonderfully thorough piece Everything You Don't Know About Tipping explains what tipping in the US is about.

Unless a server was actively hostile, rude and offensive to you, it's not right to deprive them of their income. That's just how it works in the US.

Furthermore, as is mentioned, if they get good tips, servers see it as a reflection of their good service, but if they get bad tips, they see it as a very poor reflection on the tipper. The tip on its own is therefore not an effective means of communicating your satisfaction (or lack thereof) with the service: tipping below 10% is depriving the server of their income (which they deserve even with what many might consider "subpar" service), but tipping above that is still in the range of what people might give for ordinary service, so your intentions are left unclear.

You can certainly tip on the lower end of the acceptable range (15%, or a bare minimum of 10% if service was truly bad), but keep in mind that this is meaningless unless you communicate your dissatisfaction clearly using words. Speaking to the manager is helpful for all concerned: the manager is aware of the problem, the server gets the opportunity to improve, and you have successfully communicate your dissatisfaction. In fact, you may even receive a gift certificate.

To answer the more direct question: Certainly don't base your tip on the quality of the food, but don't base it too strongly on the quality of service, either. It's just not that helpful for anyone. Consider it part of the price of the meal; don't spend the meal judging the server; and if at the end of the meal you have strong opinions about the quality of service, communicate that directly.

While in the US, you should definitely tip. This should only be based on the service; you're tipping your waiter/waitress, NOT the cook. I generally use 20% as my starting point, if I don't feel that they did a good job I'll drop down to 15% (or further if need be). Likewise, I'll go up to 30% if I feel like the server really earned it. In almost all cases, this is their paycheck. They DO need to earn it, but if they do a great job, let them know.

If the service was seriously lacking AND the place wasn't obviously busy (we must take that into account!), I'll drop the tip to 10%. However, in this case it's also appropriate to leave a note with a 'tip' on how to improve. Keep it positive, constructive criticism, be nice.

I have used the penny tip before. But for something like that, the server has to pretty well straight out offend me. It's not something reserved for poor service.

Tipping aside, keep in mind that you CAN speak with the servers' manager, about their performance. I will stress with this statement, that if you have an amazing server, that's just as important to convey to the manager as well, so that they can be rewarded for being awesome.

In all but the most exceptional circumstances try to tip between 10-20% (even 10 is a bit low) however certain scenarios would definitely lean towards not following this standard, keep reading for my own personal example.

I went to a Chili's restaurant for dinner, it wasn't busy at all and we were seated immediately. Our server took our order and then we never saw her again, another server dropped off our food and no one ever came to ask how it was or check if we wanted anything else. Finally we ended up needing to walk up to the hostess to get and pay our bill; we made a point of not tipping at all.

A feedback to the managerial staff of how the waiter/waitress served you will do it I believe. However it the food is great surely leaving a tip is something that can be consider, since in the kitchen there are some dedicating cook that are making everything they can to put a smile on your face when you're leaving the restaurant.

Just for additional information and warning:

A lot of restaurants in New England and along the Canadian border will add an automatic 18% gratuity to your bill. This means they've decided how much you're going to tip and put it on your bill.

They will always tell you that they're adding it, or forewarn you that it will be added... but only ever in small print. A lot of people don't notice and tip twice. Servers will never turn down two tips on the same bill.