3. What format are you shooting for?
Switching platforms can be hugely detrimental to your development. You'll want to have a great idea of the systems you want to develop for and maybe even think ahead about support for your code later. Smaller teams might want to limit their reach at first and then move onto other platforms later, but you need to know where to start. If you can, be specific about the kind of graphic hardware or other hardware your game might require. If you want to go overboard, jot down the minimum hardware you want your game playable on. Use specifics: PC, iOS, Android, screen sizes, required graphics detail, etc.