I think it's very simple. You've gotta be an interesting person to have interesting conversations. As Simple As That. It's like playing a sport. You can't walk into a soccer field wondering how can I be a good player. You've gotta be a good player..
Which means you need to read, meet lot of people , have some interesting experiences, hear amazing stories and be able to bring all these together when you meet someone... And then it becomes a virtuous cycle from there on... Trust me that's how it works... :-)