He got them at the front door as customers registered if they wanted to. Then they have already been a customer and get all the latest info emailed to them like a fan club.
If you wanted to be aggressive it would be to register for some big prize like sending a coffin to your mother or having your very own something or a free something or a discount or a news letter. Some percentage of those will return when notified. Some percentage will by a T-shirt on line.
It's better than them forgetting what happens in October, oh yeah I was going to go to that but, I forgot. You simply say by registering you will get coupons or be notified where to get them to print out or pick up at a sponsors location.
However, you could be a spammer? If they genuinely did not want info updates.
Another fabulous post from the U.S.Department of Wild Imaginings, now in spectaclar stereo, sponsored by the Adhesives and Sealants Council, suggesting ways to stick things together since the 1800s. Not fabulous in a gay way. Your results may vary. Illinois residents add 8% sales tax. These posts have been made by professional post makers, do not try this type of posting on your own without extensive training, lovely assistants and a trusty clown horn.