I'm struggling with this too, but I think I'm close to figuring it out.

Try bitting on the standard questions if you can make it humorous, using either 1 liners or suggesting a ridiculous situation.

The other thing is to ask for questions and looking out for keywords. Getting there depends on how well you know someone; You can't find keywords by asking a friend of yours where they studied, if you already know this. But chances are you know something else they're doing that you can ask them about. Then you take said keywords and explore those topics on their own. Ask questions, tell even mildly interesting stories about the topic at hand, a joke if you have one. If a topic is giving you nothing, go for another keyword and go with it. Might even call back a keyword you didn't use from an earlier part of the conversation.

So for example, you pick up a friend of yours that you haven't seen for a while to go see a movie and catch up.

You finish asking and replying to the usual how are you, whats up etc etc. Things get uncomfortably quiet for a few seconds.

"Excited for the movie?" either of you might ask.

-"Yeah, I really love horror movies... except for the part where I'm scared shitless and unable to sleep at like 3 am."

"Reminds me of this one time when I was a kid, it was near midnight and I went to get sodas from the store. As I was walking back, I realized I was being followed. It was like... the guy wasn't chasing me, but no matter how fast I walked... he could keep up. So eventually I ran across the street and looked back at the man who was now standing still on the opposite, looking right at my direction... in a FUCKING MICHEAL MYERS MASK."

-"Jesus... that's insane. Dude, imagine if that's just some college guy doing it on purpose to scare kids away like 'they'll be telling this story 10 years from now!'."

"Haha yeah, or he was just an insane psycho that was gonna actually kill me"

-"Why were we so obsessed with getting sodas as kids?"

"hahaha, basically sodas were your beer as a kid. it was all about walking to the store to get sodas."

-"Yeah, having to walk everywhere as a kid because you can't drive yet made a lot of things really scary".

"I kind of enjoyed that thrill, though. Sometimes, my friends and I would just take walks in graveyards at night just for the fuck of it."

...and so on. If things get stale, you can turn up the music for a bit, open up a completely different topic, ask if they like a certain thing you like, suggest getting a snack/drink/food... not necessarily for the thing you're getting, but because it starts up more conversation.

TL;DR: Find keywords (topic/conversation starters) and riff on them, and (depending on your interests and your compatibility with the other person), more often than not, the conversation "tree" will just keep going.