Whatever it takes to get there, just keep an eye on the temps. Some chips might get there on stock volts, others might need 1.5v or more. Personally I like to stick to the 10% rule with vcore which puts it at 1.45v for a B3 Q6600.

The proper way to go about this is to OC the FSB in small steps and test for stability each time. Only bump the vcore or other voltages when needed. You stop overclocking when:

-you reach your desired speed
or
-vcore is at the max safe limit (1.45)
or
-temps are at the max safe limit. (under 70c fully loaded)

What is "safe" is highly debateable but that's my opinion on it.