I'm just about the same. If I get outstanding service, I tip very well. If I get lousy service, I still tip decently, unless the waitperson was personally rude or combative. Then there are no rules - I might actually pick their pocket.20% or $5 at minimum, whichever is greater, up to 30% for great service.
I also tip extraordinarily well around the holidays, because I just feel like it.