I'd set up a basic story prompt, describing the roles and personalities of my character and a few NPCs, as well as relationships between all of them. I would then introduce my idea in form of a role-play, usually with my character blurting it out - then let the language model fill in reactions of other characters. From then, I'd just play along with the story.

It wasn't the most efficient way of extracting commentary out of a language model - particularly out of one that was optimized to generate plot twists and setting changes instead - but it was a very fun way.