First off i set the fan to a point where i cant hear it above the noise of the rest of my rig, on manual, which is around 59%
Then i move the sliders mem/core/shaders up a bit at a time, 5-10 points or so. At first keep the mem/shaders linked. After every 5-10 you go up, test it by playing a game, or a crysis bench, or 3DMark or something, or all three (3DMark might run fine but games may have artifacts/tearing, so its best to test on a range of apps). Do the core/shaders first, once you start seeign weird stuff, or crashes, move the sliders back 10 points or so, unlink them, and move them seperately untill it happens again. Move them back 5-10 to a "safe" level.
Move onto the memory and do exactly the same again, i find mem usually cant be pushed as far.
Also, as above, do your own research first then come on here with specific questions that can be answered without people feeling like they have wasted their time. Your lucky work is slow this morning.