If there's one trick we've heard marketers rave about, it's this one. It's called a shopping cart abandonment campaign. If a customer changes their mind before completing an order, they automatically get an email encouraging them to finish the purchase. You might include a simple reminder (in case they were distracted before completing the purchase), or offer 10% off or free shipping if they come back and buy the product. Most web sites do nothing, we're told. Of course, you need the shopper's email address, though you might have this if they had to "log in" to make a purchase, or if they're already members of your site.