Hi aznlilboiz..
Each video card is different for over clocking, and the only real way to find the best solution is to test it yourself. I recommend not overclocking the video card...many bad experiences with doing that
However, to overclock, probably the best way to do it is to let windows detect the best setting, and then if you want even more, increase it by small incriments.
Test each jump thoroughly and make sure you're not getting any artifacts on your screen (little wierd things that shouldn't be there).
Hope this helps, and good luck.