A few things than can be done to make someone feel at ease vs. feeling like a failure of a conversationalist .. once in a while .. (when one is feeling extra generous maybe?)
Nod along:.... or at least raise eye brows once in a while. This assures the 'talker' you haven't died of sheer boredom at their stories and encourages them to continue to tell you more. When you give the 'talker' the very serene yet very blank look, it's the non verbal equivalent of saying "Bugger off, you're stories are BORRRING, I don't want!"
(Unless you want them to shut up, in which case, staring stone like at them should pretty much do the trick)
Smile: ....maybe, just maybe, offer a hint of a smile when they're trying to tell you funny things or trying to amuse you? Bridges are usually built in this manner with unfamiliar people. It's laughter that brings souls together at least in the beginning of an acquaintance, so dole it out in generous amounts. Too tough? A mere smile then? Thanksverymuch! We all know expensive they are .. so thanks for sharing ...
(Unless the 'talker' has an appalling unfortunate sense of (non) humor, in which case you really shouldn't be around them too much, and the stony expression is SO the way to tell them that. You keep right at it! Bravo!)
Contribute: ... meaningfully so: You know how they taught us that to be successful at group discussions, one needs to take off from where someone else left off so it offers the illusion that you were actually listening? Surprisingly, the rule doesn't only apply to GDs when you're cracking B school processes. It also applies to real life situations, so apparently when someone says A ... I must try to say something that's connected to A (hopefully A isn't so dreadfully dull / esoteric / complex/ irrelevant that I can't possibly think of a way to contribute or build off it) and that's how it all works! Brilliant!
(That's when we call it a conversation btw .. when we talk to each other ... not when we talk alongside each other... that's just a dual monologue ... NOW U know :-)
I'm just saying, you know ...