In order to pick a concept for a game, I like to start with the main genre and I want to talk about. Think of an episode of the original Star Trek. It is a Sci-Fi show, but some episodes had mystery and intrigue, others were set in a historical (like) setting, still others were straight out of a horror novel. Overall, the main genre was Sci-Fi and that is where I start to pick my game concepts.
Stay around until the end of the episode to hear about a game that you and your players can play a month or more before your next campaign to get their involvement in planning it. For more of an in-depth look at this game go to the website.