Talking about amd systems, without any knowledge about the intel:
When i oc, i do it in small steps, about 100mhz on the cpu. If i go too far, it 100mhz wont damage my computer but there will be notable mistakes, freezes, program crashes etc. My phenomII 955 runs at 3.2 GHz by factory default, without any overvoltage i could push it up to 3.8. After that, overvoltage is needed to maintain the stability, but that means a LOT of extra energy consumption and my supercheap PSU cant handle that.
What i can say: be patient, dont try to push it up to the limit in 10 mins. Do it in small steps, only overvoltage if you have a very capable cooling/PSU. Its valid with the video card/ram/mobo too. Test your system after every step, if you see anomalies, let it be any small, step one back. Also check the temperatures at full throttle, i never let mine go over 50 celsius (not the cpu, chipset, gpu or RAM). In this case, you wont damage anything yet will get about 15-20% inprovement.
Good luck