When I opened the new site, I sent an email to customers on the email list for the old site to let them know about it. I made them a special offer. If they referred a friend to the new site, they would get a credit of 5% of that friend's purchase, which they could then apply to their next purchase. There was no limit on the number of credits, so somebody with a lot of friends could get a pretty good discount. Nobody took me up on the offer.
Maybe 5% didn't seem like much, but it's half my profit.
I'm constantly brainstorming new product ideas, but can't come up with something that hasn't already been done a zillion times.