Using EVGA overclocking tool. You can make OC profiles & you can active them on the fly, using a simple button combination which every user can choose .Based on the Riva tuner core.
You need a program like Coolbits which lets you manually adjust core clock and memory clock frequencies. It isn't safe to overclock and it usually makes you loose the guarantee.
I feel that one of the most efficient ways of overclocking a nvidia graphics card is through an application called rivatuner! Which is downloadable for free from the internet.
