I don't like to talk much, but people love to talk about themselves. Ask pointed follow-up questions so people really feel like you're listening.
Guy: "I study molecular biology."
You: "cool! I work at a bank."
That shit's not going anywhere.
You: "cool! That's one of those things I've never really learned much about, what does that mean?"
Now he can talk about it more, you can ask him what he likes about it, etc. And you didn't need to know anything about molecular biology to go there. If you do know a tiny bit about something, that's also a good launching point. "Cool, my brother's friend skydived, he told me they really should warn you about the way the wind blows up your nose. Did that happen to you?" will give him a great chance to point out something hilarious to impress you. And you still don't have to have had any experience.
Also keep in mind the way you say stuff in a new setting is almost more important than the things you're actually saying. You can have a bland-ass conversation that isn't going anywhere but if you look like you're interested and you get him to talk about a few things he didn't expect to talk about he'll still have fun. I will never forget a conversation I had with a drunk guy who seemed fascinated by my master's thesis. I'm pretty sure he didn't understand a damn thing but it really seemed like meeting me was a "holy shit, I can ask this guy that stuff I've always wondered about!" moment. That was still a great conversation because every time I thought there was no way he was still with me he had a pointed follow-up comment or question.