When people hand you their business cards, what do you do with them? What you DON’T do is add them to a bulk email list. Aside from that, you still want to keep in touch. Here’s a process that works for me.
The woman I met at her promotional table can’t follow up with me. She gave me her card, but she never asked for MY card. Having my card in her hands would have allowed her to follow up with me. I like being in control, but it was a missed opportunity for her.