Beyond Blender Render/Draw, Draw, Draw, Write, Write, Write
Drawing Will Draw Up The Game edit
If you want to get stuff down before getting to work and forgetting it get a piece of paper a pencil and a clip board. Draw up the GUI (the graphical user interface or menus and HUD), the level maps, the stuff that might count as background. Write stuff up on files you may need, stuff you want, and your Christmas Shopping List. You don't have to get this done before on computer development, in fact you don't even need to do it at all. Just it helps. Remember. The larger the game the harder it will be to remember an make. SO MAKE IT LARGE!
Discuss, Argue and Fight edit
Discuss stuff about the game. Think about what you want in it, special pick-ups, challenges and more. Try to decide on what you all want so as to make sure you don't argue and none of the stuff works. Have a bed fight if you want and this might even end up in the game. Be inventive.