Hello!
The type of loyalty program I have planned is a “Loyalty Card” that is about the size of a business card. On one side it looks almost like the front of a business card, and on the other side there are 10 squares and certain ones have the promo. Each time the customer purchases you stamp one of the boxes. My promo card on the 3rd visit they earn a stamp on a space that says “1st offer, free stuffed crust”. They can only use that on their next purchase. Then in the 6th space they earn a free small pizza after the 10th one, a free large pizza. Just an example and the card does have a expiration date, and can only be used once.
A lot of places do things like this here where I live. Some you need to fill all the spaces and in the end you earn something but most are progressive where you can earn something small like a free cookies/soda after the 3rd visit, and earn higher rewards later in the card. Expiration dates are important =)
Hope it helps!