As most PC enthusiasts and builders have noticed today, CPU makers have made overclocking a CPU pretty easy in comparison to days past. It is no longer strictly a "geek affair" to overclock a CPU. For the most part, the days of messing with raising the FSB(Front Side Bus) which also messes with RAM timings, chipset timings, etc are over for casual overclocking.
Today, CPU overclocking is usually as simple as raising the multiplier and testing it. AMD and Intel both offer unlocked "K Editions" (Intel) and Black Editions (AMD) that make overclocking a relatively easy process. Infact, Pretty much every AMD CPU you buy nowadays are the unlocked variety, while Intel usually charges a slightly higher cost for their unlocked versions. However, if your were already going to buy the Intel CPU, your usually better off to get the unlocked version anyways.
That being said, below I will outline "my best practices" for overclocking and stress testing CPU's that I believe to reasonable and successful. This guide will go against the grain in the stress testing department simply due to my years experiences, trial and error, etc and what I have found works best for me. I hope this guides gives you a good baseline to work from.