Set up your loyalty program
Reward returning diners with points they earn on every order and redeem at checkout.
Set up a stamp card
Run a "collect N, get a reward" card, like buy 9 coffees and the 10th is free.
Create a discount code
Make a promo code diners type at checkout, with limits on use and expiry.
Track and turn off discount codes
Read a code's status and redemptions, and deactivate one when you are done with it.