Beyond the added cash, though, maybe just try a little empathy. Both of the delivery guys we spoke to said the biggest thing they'd ask customers for is patience and understanding, with one of them saying "When the weather's bad, sometimes we can't take the delivery in 10 minutes like usual. Sometimes, we can be a little late, and they get mad." Yep, we get mad, because their food's not there in 10 minutes during a downpour. Meanwhile, the GM at Lombardi's had these parting words: "When you tip, take into consideration what it takes to get the delivery to you. "
Patience, in other words, can be just as valuable as your tip. But you should probably tip more anyway.