|Simple enough, just answer 6000 questions correctly. This counts across all game modes including Xbox Live. You can view your progress by selecting report card on the main menu.|
Turbo controller method: If you have a turbo controller, such as the Street Fighter IV controller, you can get this quite easily. Setup a Battle of the Wits Match on easy vs the cpu. Set the Controller to Turbo the A button, or if you don't have a turbo controller, put a piece of scotch tape on the A button. You will answer about 800 questions an hour right, and it will auto rematch as well.