I agree with LPCurse! Make sure you have your idea written down, plan out the mechanics and how you'll implement them into the game, and, if you can, find a great team to work with who have different skills so you don't have to do the narrative design, art, music, etc (unless you work better that way!). For many game engines, however, there are a ton of free game art/music/scripts available to lessen your workload and help you achieve your vision.
Good luck! :)