I know that around here servers make like, 2 bucks an hour, so I always tip at least 15%. I tip more if we hold up the table for too long, or if we order cheap stuff and 15% of the bill comes out to like, 2 bucks (it’s not the waiter’s fault I just wanted water and my friend didn’t want dessert).
I give the pizza guy about 5-10% because I always assumed that the delivery charge was his "tip", but this thread has debunked that theory, so I'll tip more from now on.