Overclocking is all about Temps and Voltage. The cooler you can keep a chip, the better! The cooler the chip, the less VDC needed to power it, meaning less heat. Oc'in way above spec needs more voltage so be cool! Yes, it's a vicious cycle!
After that, it's memory dividers. Lotsa Fun!
Quality of hardware is paramount.
When you've achieved your 24/7 OC, you may run into problems with your onboard peripherals, (NIC, Storage) etc.
I recommend reading and researching the hardware, and people's X-Periences! (forums) IE: No Particuliar Order
i) X-treme Systems: X-tremely crazy about pushing hardware to the limit!
ii) Hardop: Not quite as

iii) HardwareCanucks:

iv) Ncix: Good support from most of the regulars, once again, watch out for the nuts!
Definition of a Nut: Someone who takes the latest and greatest hardware, and reduces it to a smouldering mound of silicone in under 24 hours!