Watching this video will help you avoid the VERY common pitfalls that indie developers seem to land in while making Greenlight projects. This video will in no way guarantee you a successful project, but it will guarantee your project (not the game) wont suck.
Follow the steps but mold them to your needs. It's not a rigid guide, but not fulfilling these categories is going to be counter productive to your attempts at pitching the game to the Steam community.
Good luck Indie developers.
