The 'best' is the highest core and memory that your card will do and remain stable in all 3d applications.
There's sometimes a very narrow band in the top end of the card's range of it's ability where it will actually lose performance but still remain stable like this:
950MHz : Fastest
955MHz : Slightly slower than 950 but still technically 'stable'
960MHz : Crashes
But that doesn't happen w/all cards. If you just find the highest stable point and back it down by about 10MHz you should be at the 'fastest' point.
Perhaps Ryan is unaware since he has an older card, but with Fermi cards the core and shader are locked at 1:2 ratio, so they always OC together.
There's about a million guides on the internet that explain how to OC a graphics card so I'm not going to re-write the book on it. Just look up a guide on OC'ing Fermi or 400 or 500-series nV cards, the process is the same for all.
One last thing: a lot of overclock guides rely on stress-tests like Furmark or Kombustor ... personally I find these will cause you to think your card is stable at a higher clock than it really is.
So make sure you do some benching runs as well: a couple loops of 3dMark11 and/or Vantage, along with a couple loops of the Heaven bench, maybe a Crysis bench run or two ... Is actually a lot more 'telling' than any stress-test, IMHO.