The best stories for this event have a strong plot and dialogue. Something has to happen and there needs to be a change. The more ready your story is, the better chance you'll have being cast for the show.
Note that you will have limited creative say in the outcome of the film. You have to be ready to tell a story that you can let go of. You may our may not like how the film turns out, but if you go into it with the right attitude, it's fun to see how it's interpreted by the team. Chance are it will, almost always, be wildly different than you expected. Also note that most of these filmmakers are to different degrees amateurs, still learning the craft of filmmaking, and they are working with very small budgets.