I always assume the delivery surcharge doesn’t go the the person that brings me the food, but pays for the packaging and shit. I guess my tip depends on the size of the order and such. On a typical order of a couple of pizzas it is usually 5 bucks. If it is something weird like 20 pizzas, then it is a larger amount. I don’t really go by the bill and a percentage, I more try to guess how much of a pain in the ass it is for them and adjust accordingly.