You'll go hunting on the internet for a Promo Code and may come across postings with promises of hundreds, even thousands of Shopkick Kickbucks just for entering their code.
I do remember seeing that there is a time limit in which to enter the Promo Code.
You get 50 Shopkick kickbucks and so does the person from whom you got the code. (it reads as much on my promo code screen)
Here are the FAQ's from the Shopkick site.
Here are the Application TOS
Here are the general TOS
Here are the mobile TOS