So I'm currently working on a pathfinder conversion of The Dark Sun Campaign setting and I've been mulling over something new to me, the Idea of allowing The PCs to decide what direction to take the campaign. Decisions all made in game of course. Here is how I’d try and accomplish it; whatever they decide to do/be mercenaries, dune traders, rebels etc. I'd try and build an appropriate adventure around said direction and make it heroic and compelling. I am good on the fly and generally prep a lot before games, though you can never be sure what to expect sometimes.
Ok since I'm done rambling on my Question to you is have you ever tried running a freeform game like I described and if so were there any unique curveballs your players tossed your way? Additionally if you have pointers about running a freeform game they’re always welcome. My main concern is players wanting different things, but my group generally gets along and works together well.