Making con friends?

Maybe this is the stupidest post ever. But I often hear, from my own friends and among other social medias, about people meeting up with "con friends" that they met at DragonCon and only see at the con.
and I'm over here like, how?
I mean, I talk to people at the con and have enjoyable conversations. But somehow never manage to get it past brief pleasant conversations in lines.
Is there something wrong with me or do I just not know how to make friends anymore?
How do ya'll do it?