The Wellsprings of Creativity

How to come up with ideas for a game? I'm not sure that's the best question. Don't prep plots, prep situations: I think the best advice is to create a sandboxy world that generates material, rather than have to create a fresh 'plot' every week. This will depend a bit on the game and genre - a Call of Cthulu game is likely to lean more to plot than sandbox; a military game is likely to be mission-centric. But even TV shows have leaned more to sandbox approach in recent years, with plot continuity and a big cast of motivated characters who can reliably throw up new events and characters. While fantasy is the traditional home of the sandbox, space opera and super hero genres are equally well suited - you need sketched locations, strongly motivated and active NPCs and factions, and preferably some procedural content generators - encounter tables, event tables - to kickstart your own creativity.