You can indeed!
EVGA even offer their own software for this very purpose!
http://www.evga.com/precision/
Start off with a very, very low overclock, and increase it until games become unstable. At that point, downclock it a bit and make sure it's all running swell and stable.
Personally, I see no need to overclock an Nvidia card anymore thanks to the Boost technology in them. They already overclock quite a bit to hit it's thermal and power headrooms (My stock 760s overclock themselves to 1150Mhz, with me having done absolutely nothing).