Start by maxing out power target. By maxing out power target it'll allow the card to use as much power as it needs. Next, up the gpu clock by 25 Mhz and then test for stability using a program like Heaven 3.0 with maxed out settings. If it passes Heaven, up the overclock and run it again. If it fails in Heaven then lower the overclock 5-10 Mhz and reboot the PC. Run Heaven again and if it passes then that's your card's max gpu overclock. Do the same with memory. I would leave voltage stock. Voltage, if you're not careful can kill the card. Each card is different so there's no way we can tell you which values to use. Test and enjoy!