Originally Posted by Droogie
It goes down in .0001 intervals.
Personally, I start raising clocks until I either lose my display, crash, or see some artifacts. Then I will proceed to bump the voltage a notch. Rinse and repeat.
It's nice to have the lowest possible voltage while maintaining complete stability so you can keep your temps down.
This is just how I do things. If your overclock is stable with your current voltage, then you can do the process in reverse (but leave your clocks the same). Just decrease voltage until it's unstable and then set the voltage a notch up from that. I would jump by .005 (e.g. 1.075, 1.070, 1.065, etc.).
Hope this helps!