First you take the phonecalls by clicking on the phone icon when it appears. Prepare the pizzas that the customers wants, and when they are ready you can drag them to one of your delivery boys. Click on the customers order so that a blue flag appears. This way the delivery boy knows where to go. Only when that is done should you click on SEND in the delivery boy menu. If you work fast enough you will get a tip. Click on the money to pick it up.