How to write thank you letter after customer visited booth?

What sort of thank you letter would YOU like to receive? Go along those lines, I would keep it short and sweet

In the past when I set up booth sales, I would generate a mailing list from each booth sale. I would then send out purchased, boxed Thank You cards which were blank inside. On the inside I would hand write a quick note "Thank you for purchasing (product name)" or "Thank you for your interest in (product or company name)" Depending on the customer, I would also include either a small product sample or discounted offer for their next purchase. And always included my business card.