My maternal grandfather influenced my tipping practices, even though I was 17 the last time I ate a meal in a resturant with him, as he got sick and died in the late 1980s.
He used to say "Mitch, these waiters and waitresses depend on tips. They don't make much in salary. You need to tip well." I dont remember exactly what percentage he gave, but, I know he was always a generous tipper.
I eat at many all you can eat buffets here. As I understand it, standard practice there is to tip $1 per person, even if the meal costs only seven or eight dollars.
I know that the "standard tip" is usually 15% in a diner, etc, and 20% at a good place. I usually split the difference at a diner, and.. give.. 17 to 18 percent on, say a $15 meal. At a more expensive place, like... the Outback, or a really fancy place, I tip 20%. When I took my father out for his 60th bday, at his favorite fancy chinese place in NY, Shun Lee Palace, our bill for lunch was $75, and I gave the guy a $16 tip, a bit more than 20%.
I have one friend, who infuriates me with his method of tipping. If he doesnt like the service, he'll say.. "No tip". This especially bothers me if he does it down here, in a place I'm known, and that I go to all the time, so,, if they see me the next time I eat there, they can be like "There's the guy who was with the asshole who didnt leave a tip".
Anyhow, back to the point of the thread, I usually tip between 15 and 20 percent, always, unless I have a particularly rude waiter, or terribly bad service. My grandfather taught me well, I believe.
Mitch