Before hand on anything, you're not going to have a real successful overclock without raising the vcore a little. Pump it up about .10 volts, see where your temperatures run both idle and under load. If you are hitting under 50C both ways, you're in good shape to give the memory a few more clocks. Besides that though, if you have the equipment to handle the heat, check out an unlocking guide for your chip, put the vcore to its highest (probably 1.85) and go at it. With a free multiplier, and an extra 1/5 of a volt, you should range about a 250-700 overclock. Just beware, the heat is what is going to make anything unstable.