The tip is not any of the following

1. ONE DOLLAR
This is a popular mistake. It has caused some customers to tip $1 no matter how much work was involved. It might be a bigger order, the weather could be bad, or it could be a longer drive. The tip is really 15%. The $2 minimum is polite. A $1 "tip" is perceived as an insult if the order is $20 or more. For example, on a $21.19 order, one dollar is less than 5%.

2. LEFTOVER COINS
Suppose the total was $14.83. The customer gave the driver $15 and said, "Keep the change." That's only 17 cents for the tip. Anything under $1 is considered leftover coins. This is considered an insult to the driver. It's a small fraction of the standard amount for the tip. Now, if you want to tip a few bucks and add the leftover coins to it, that's no problem at all.

3. ONLY SAYING HOW MUCH YOU APPRECIATE THE DRIVER
Saying how much you appreciate the driver, the pizza, and not tip is called a verbal "tip."
It's the same as no tip, except the customer notices you should be tipped and does not.
This is perceived as hypocritical and cruel treatment.

4. INCLUDED IN THE BILL
Some customers don't tip because they assume it was included in the bill. The tip is not included, even on large orders. Even if the order is $500, the restaurant did not include the tip. The restaurant can't put the tip in the bill. You can, however, add the tip to a credit card payment in advance when you place the order. Exceed the bill or tip separately.

5. INCLUDED IN ANYTHING FREE
With free delivery, drivers still depend on tips. "Free delivery" is an oxymoron. Pizza companies should not mislead the public like this. It only means the store does not charge a fee for delivery. "Free" refers to what the store charges. This has nothing to do with the drivers. They are tipped employees. This also includes open bar... free liquor doesn't mean you dont' leave a tip to the bartender.

6. INCLUDED IN A DELIVERY
Very often, it does not go to the driver's tip. It usually goes to the store. The driver doesn't get one cent of the delivery charge. It could go to the driver in other ways, as mileage compensation or hourly wage. This is not the tip. If some of it actually goes to the tip, you may reduce your tip by that amount. The idea is to have a partial gratuity and let customers tip over it. Please ask the store about how they use the delivery charge because it varies from store to store.

7. DELIVERY VS. WAITSTAFF
In a personal observaton, people seem to tip a bartender or waitress much more than a delivery person. This seems rather unfair to me since a bartneder walks two feet to get you your drink and delivery person picks up your food, drives it over to you, parks, walks up stairs and has to drive back. Bartenders & waiters don't usually leave their building to service you, so next time, tip based on the effort of service.

One last thing you should consider when leaving a tip. Most tiped positions usually pay below the minimum wage and the person servicing you almost always has to tip out another person such as a barback or busboy.

I hope this gives you a bit of a guideline on when and how to tip. The folks that work in the service industry work very hard to make sure that your experience is a comfortable one and they should be compensated as such. So never guess if your tip is enough, always give a little bit more and then you never have to worry.