It isn't as simple as putting in a frequency and voltage. When overclocking a CPU, you'll be increasing your CPU's clock speed bit by bit, from 3.2 to 3.3, then 3.4, and so on. You raise your CPU's frequency, then run a stress test to see if it's stable. If it is, great, try to clock it even higher. If it isn't, then you raise the voltage bit by bit (to a reasonable level) till it is stable. If it won't even boot after dialing in an OC, then either give it more voltage or give up. And you must be sure to not throw too much voltage at the CPU. Too much and it'll die. Older AMD stuff will take higher voltages than intel stuff, but the rule still applies. From what I've seen 1.55v is the max for those parts. But try to keep it as low as possible, and only increase it in the smallest increment possible. Hope this helps some. You should also try looking for a video overclocking guide, you may not find one for Phenom II parts specifically, but I'm sure you can find one that will help you out. You've also got to make sure to keep your temps low. 60C under load is pretty well the max, under 55 is good.
EDIT: Read some more, looks like most people consider 1.55v to be the max. But 1.5v would be a good place to call it quits if you've got a good speed out of your chip.