I have my mouse at whatever runs normally in Windows (providing your mouse sensitivity in windows is around normal). Using the MX518, for me that's 800dpi. It's best to run it low, and then tweak the mouse sensitivity in-game because that would give more accuracy than if you'd change it around and play some super high dpi and then tone it down in-game. You could get the same accuracy on a 400dpi mouse probably, but if you'd play high sensitivity with that, you wouldn't get as much accuracy.