If the service is not good, the person is lazy etc, no tip at all. It has not been earned.

If the service is good but not better than average I tip 10%.

If the service is excellent - as much as I can afford as high as 25% for outstanding service.

I do give the PH a tip for staff if they have earned it, beyond that if service is outstanding I also tip directly and always if I have asked the staff member to do something for me like if I ask the skinner/butcher to find my bullet.