Next time someone tries to give you a business card, politely decline, and offer to send an email right then. It gives you several advantages.
The first is that their contact info is now easily searchable by you and the person. The second, more important advantage is that you can insert an actionable item right there in the email if you and the person have agreed on one. 
Lastly, because you’re doing this immediately, you’re less likely to forget a. to scan their business card at home b. after scanning business card, to email them c. what y’all even talked about.
 In 90% of cases, if you don’t have an actionable item after meeting, it’s probably not worth your time to keep the contact.