Most require you to fill out a form, they "process" it, and then you receive your card(s) in the mail several days later.
On the plus side, this weekend I used my Randall's card to buy gasoline. The normal deal is 3 cents off per gallon, but this one store had a double discount going, so I paid $1.26 compared to the regular discounted price of $1.29, below the $1.32 a non-card customer would be charged. No other gasoline seller in the area has regular below $1.31.