Before you call in an order to a delivery restaurant, make sure you write down everything everyone wants. That way, the ordering process will go a lot easier, you'll be more likely to get what you want, and the restaurant can start preparing your food a bit quicker.
Most delivery restaurants also offer pickup options, which can be a lot quicker and a bit cheaper. Even if you don't get a break on the price for the restaurant, you don't have to worry about a tip for the delivery driver -- and you don't have to wait for a driver to get around to you.