In the Game Design Dos and Don’t Manifest, available on Gamasutra.com, they offer some great advice:
"If you're just starting out, think small, then think smaller. If you start on something big you won't finish it and if you do you'll be burnt out and probably won't make another. A filmmaker never starts his career with a blockbuster movie. One of the easiest mistakes to make starting out is letting ambition drive you down a path you're not ready to travel. Slow down, take your time and start simple. Prototyping is crucial for all designers."