Instructions
Start the game and navigate to the "Create a class" screen.
Choose a custom class to either edit or create, such as "Custom 1" or "Custom 2." Scroll down and click "Perk 1." Click "Lightweight."
Scroll up and click "Primary." Choose a lightweight gun, such as a SMG, for maximum speed. The "Lightweight" perk will boost your speed regardless of what weapon you carry, but a lighter weapon will augment your running speed. When in a game, click down on the left analog stick on your PS3 controller to begin running.