You will find an overclocking section in each of the PCU manufacturers websites. They advise against it usually but will give a lead. There are also O/clocking 'specialist' sites but they ALL warn against being too ambitious.
Why? Because it starts off really well, and you feel pleased with your efforts. Then, one day, you will find your PC freeze with a vengance and you CHIP firmly WELDED to the motherboard. Doesn't always happen of course, but I have seen it.
IF you must overclock, change the size of the fan at least. But CARE is the name of the game!!!! BUT, its a personal decision, and I for one would not be guided into doing it, just weigh up the pros and cons.