Anyone? No one OC:d their GPU?
Every single one is different. Whereas with Intel CPUs, the differences are in minor voltage tweaks across the 4.0GHz spectrum, and then extreme rare cases being able to hit above 5.0 with air/water. You could have two 560Tis, and one could go to +500MHz, one can't OC at all. It's a lot more dependent upon silicon lottery.
Since the differences are so vast, there aren't really any guides per se, you just need to work through it. In general, this is how I do it.
1) Increase core clock until unstable.
2) Increase voltage until stable
3a) If just benching, not trying to get a 24/7 clock, continue Steps 1 and 2 until you can't go any higher.
3b) For 24/7 clocks, Repeat step 1 and 2 until temps/noise are not enjoyable.
4) Increase memory clock until unstable.
5) Once unstable again, scale back until it is stable.
I use a single run on 3DMark11 to determine these steps. Once complete, I run Uniengine Heaven on loop for a few hours to check for rock solid stability.