My tip would vary depending on the service. Too many factors - #1 being the attitude of delivery driver. If they walk up to my door, just say the price of the pizza and expect me to give them a tip for that service, I'd give a buck, maybe two in some cases.
But, if the person is generally friendly, says the typical "How are you doing?", and other chit chat, tip would get bumped to at least 4-5 bucks. Friendly customer service is good. I know when I deliver, I try to be as friendly as possible. I repeat the order at the door just in case there's any kind of mistake, I'll be able to catch it early.
Now, if the driver is cute...and friendly - 6 bucks
