HEXUS.net - Guide :: Intel Core 2 Duo basic overclocking guide for beginners : Page - 1/9
Look up the thread this article came from in the hardware forum for more info - written by Clunk. It's a great starting point. You've got a quad, but the principles are exactly the same as they're just 2 core2duos stuck together
Good luck. My advice - go slow and steady. I can think of at least one guy on this forum who got carried away overclocking his Q6600 too quickly and ended up bricking the whole lot.