I generally tip 15-20%, but if the service is bad, then it will be less.

I've trained over 300 servers in my career. I tend to have a very critical eye when I eat out. That said, an honest effort will always receive a good tip, 25%. I don't hold the server responsible for a poorly run business, or their lack of proper service training, I just don't go back. So many things can effect service, and many are beyond the servers control. If I'm taken for granted, the tip reflects it to be sure.

I call myself a "fair" tipper. In that I mostly tip based on performance and the circumstances the server endures.

My daughter is a server at a prestigious nightclub and restaurant. So I'm very cognizant of the servers needs. I will NEVER stiff a server for any lame reason who is working on the Tipped employee wages ,often below minimum wage, even though the law states otherwise.

I tip people who give a good service or are especially helpful, but never more than 10%

I'm against it.

In many other countries they actually pay their staff living wages, so they don't have to depend on the charity of customers.

My oldest and her husband have two restaurants so yes I do tend to what would be considered in the general population to over tip.

20% most of the time. 15% if service was lacking, but not downright rude. And, I've yet to encounter downright rude service that occurred so late in the game that I didn't just leave.

Except for counter service or at a fast food place. The service isn't personal enough for a tip.

I don't think I've ever had service so bad that I felt the need to stiff a waitperson.
I know some will do it just because they didn't like the food, which is not the fault of the server.

Then there are these jagoffs.

Here in the UK there's just no tradition of tipping. It's an extra hassle. I think we add service charge onto the bill unless it's shown up front.

It's a source of discomfort and embarrassment for UK travellers to the US

My wife is a good tipper, I prefer a basic tip of, let's say, 10%, even when the service is questionable + 5% for good average service + 5% or more for perfect service. My wife normally pays the bill and gives 20%. I only stop her sometimes when the service or the food is quite bad, but I prefer sending the food back to the kitchen for a second try. When the food is questionable but the service at the table is good and friendly I don't hold (mostly) her responsible and tip her cash in person.

Here in the UK there's just no tradition of tipping. It's an extra hassle. I think we add service charge onto the bill unless it's shown up front.

It's a source of discomfort and embarrassment for UK travellers to the US