I typically tip 10% for adequate service and 20% or more for excellent service, and I get excellent service more often than not. If I’m tipping at least 20%, I also talk to the manager to praise the service I received. Terrible service? I still tip - anything from a penny to a quarter left on the table to clarify that I didn’t “forget” to tip - but bad service is rare. I’ve never had the restaurant try to lock me in to protest my tip.
Note: If the restaurant adds the tip to my bill in accordance with a posted policy, I pay the amount added (and don’t return if the service didn’t justify the tip), but I don’t tip more even if the service would have rated a bigger tip.
The standard is:
0% for horrible service and catastrophic experience.
10% for sub par service
15% is the standard for your did you job but nothing special.
20% is when something special is done/accomodation and pleasant waitress waiter.
20% as standard is pushed by the Restaurant Association in order to lower the hourly wage part paid to waitresses and waiters. IOW a net zero.