Seth Godin writes about an unusual but effective promotional idea: surprise rewards.
The typical promotion advertises rewards and often tells the customer what they must do to receive them. For example, airlines offer frequent flyer miles. Credit cards offer cash back.
But what about rewards that come as a complete surprise to the customer? Everyone likes a pleasant surprise. When the customer purchases your product, how about giving it to them for free every once in a while? Or how about randomly giving them a voucher towards any future purchase? By doing so, you create powerful word of mouth for your product.