It's generally pretty easy to figure out by the timing and also by context. You know you have three takeout orders up and you know approximately what the voices sounded like over the phone so you can take a good guess at matching a face to it. Occasionally we'd get it wrong on the first guess, but we'd always verify the contents of the order and phone number before forking it over.

And it's dead easy when you only have one takeout order open. The customer still thinks you're psychic. They won't know the other six bags lined up on the back of the steam table are all deliveries...

You also get to know all your regulars pretty quickly.