If the restaurant I was delivering for wasn't busy? I made bad less money (the people I worked for were pretty solid; you made tipped hourly + tips or non-tipped hourly during the shift, which ever was greater). If it was too busy I would be run ragged and my tips would go down as it took longer to complete orders.
To make more and more consistent money, some friends and I would 'game the system' to a degree and each be working 1-2 restaurants in the same business district at the same time. We would trade orders back and forth based on where we were going to make trips more efficient and split the payout pretty much evenly (if someone had a hard delivery or something, they might be given a bit extra).
If the restaurants knew we were doing this they would probably have fired us.
My shifts were fixed; ie I had the sunday evening and tuesday evening shifts every week. I was at the whim of overall demand; slow nights means less money. Most importantly; I could be fired.