First let me warn you that overclocking voids warranties, creates more heat, can lower the life expectancy of a cpu and can cause system failure. You do this at your own risk.
Second To overclock properly you need:- An aftermarket cooler, do not overclock with the stock cooler, a well ventialted case and a good quality power supply.
Third you need to download these programs:- CPU-z, OCCT, Prime95
Fourth overclocking should always be dome through the BIOS and not through any third party application.
Fifth Overclocking is totally experimental because all CPUs are different even the same make. Someone who has the same rig as you may not get the same results as you.
Sixth you will find that some CPUs just wont overclock much at all, usually with core 2 duos and quads you will find that CPUs with the title g0 stepping means it's made for overclocking so you should get good results.
Here is how you do it.
Go into the BIOS
Turn any overclocking option to manual.
Raise the FSB by 10MHz save & reboot.
If you get into windows go back and repeat the process.
Once you have raised the FSB by 60MHz you must run a full one hout test whilst monitoring the temps with Real Temp. You do not want to go over 60 degrees c.
If everything is ok then repeat the above.
You will notice that your ram speed also changes as you raise the FSB you do not want the ram speed to go over it's rated speed. You will be able to use CPU-z to see your ratio with the cpu and ram 1:1 and 5:6 is what your looking for.
Now you need to manually set the ram voltage to whatever the manufacturer stated (sometimes this is called DRAM voltage).
You should also set the PCIe frequency to 100.
Now save and reboot and see if you get into windows. If everything is ok you can go back into the BIOS and raise the FSB by 10MHz again. As before once you have raise by 60MHz you must test with OCCT for 1 hour whilst monitoring the temps again.
You should realise that overclocking uses more power and if at any stage you get a BSOD whilst trying to boot into Windows you need to raise the VCORE voltage. Only ever increase the VCORE voltage to the next available increment then you can try and boot into windows again.
If you have trouble with any safe VCORE voltage increase then you can try and lower the multiplier this sometimes helps but I tend not to bother, if I find the FSB hits it limit then that's where I stop.
If you get a black screen or the PC wont boot, you need to do a cmos reset and begin again.
Once you have got to an overclock you are happy with you must test with prime95 for 6+ hours whilst monitoring the temps.
There are other things you can do to help with an overclock but these steps are optional.
You can manually enter the ram timings.
You can lower the southbridge and northbridge voltage to help with heat reduction.