Calling it a "Dark Art" is not so far of as you may think, because even if you´d find a guide for your CPU/MoBo combination, it is not guarenteed that you would achieve the same results. Just a microscopic difference in architecture can mean a really high Overclocking or none at all. 4 Years back, trying to OC my still present Q6700 i ran into the problem of instable VCore. I got it near 3.3GHz, ram was working fine, system was booting up fine, no bluescreens, so far, so good. CPU temps look good, so let´s start prime. Whilst running it i noticed my VCore dropping, with the result that all calculations on Core 3 (or Core 4, if you start numbering with 1

). At first i had no clue, went back into bios, triplechecked each and every setting, let prime run again, went back into the bios, let prime run again and finally i found out what caused the problem. Whenever all 4 Cores were under power, VCore dropped from 1.4V back to default 1.325V, but stayed at 1.4 as long as only 3 Cores were under power. I just resetted the damn whole thing and never oced it again, because i couldn´t figure out the reason for the droppage.
My last successful CPU-OC is actually over 10 years back, OCing my trustworthy Pentium II 350 to 392.