One of my shops sends out an email with 30% off any one item during the month of -------. Excluding store kits, clearance items, services, and special order. Maximum coupon value is $30. No need to print anything just let us know when you check out you would like to use your coupon.
Everything is on the computer so she knows if you have used it or not.
Another shop prints on my receipt qualifying purchases up to $250 spent in the store or online I get 10% off my next total purchase.