pulled up to pay and get the food, his accomplice who was hiding near by would run by and grab the food when the worker handed it out the window. They would look at each other in surprise, he would say "I'll follow him!" purposely stall the car, giving the guy time to get away, then drive off, circle the block and return saying he couldn't find him. They would then give him his order again for free and refund him if he had already paid. So you got double the food free.
I also had a friend working at In and Out, we would go when he was working and just ask for "the special." he would then give us something free. Fries, a shake, whatever he had right there.