Creating topics is simply a matter of spotting a capture that sparks an entire story in your imagination - then writing a set up for that story that falls short of supplying all the details. You leave some out for members to fill in or you leave off the payoff for members to complete.
Not every capture is necessarily going to work for this game, but many will. And someone will know when they've come across the right capture for them because a scenario will just pop into their mind.
Then it's just a matter of picking the best words to hopefully get the set up across while also allowing several potential directions for it to play out. It probably sounds harder than it really is. But one thing is for sure: every day I'm blown away by some of the things that people come up with that I never saw coming.
So, I'm really looking forward to seeing the sorts of set up people can come up with...