Have you actually been able to set your multiplier to 60, so that you're getting a 6.0GHz overclock? That would be amazing. If you're just saying that your motherboard's OC software lets you try to set it that high, not so amazing.
Start with stock voltage settings. Move your multiplier up by 1 or 2 at a time until you reach a point that is not stable or won't boot. Then try increasing the Vcore (CPU voltage) a little bit at a time, not going much higher than 1.4 volts. Continue to increase multiplier and voltage in small increments until you reach your "wall" - the point at which you can't create a stable overclock.
Don't set your voltage too high! Try to stay below 1.4V for a "practical" OC.
Keep your peak Prime95 core temps below 75ºC and the CPU voltage below 1.4v for an everyday overclock that should last for years to come.
And I don't subscribe to the "overclock slowly in 1x multiplier steps" overclock method.
1. Set CPU voltage to 1.3-1.35v
2. Set CPU multiplier to 45x
3. Save and exit
For most Sandy Bridge CPUs it's that easy to get 4.5GHz. Once you get there, either be happy with it or you can try for a bleeding-edge overclock. That one you should do more slowly as it usually requires more tweaking.