Shoot at shutter speed way below the screen refresh rate (typically 1/50 to 1/75). Go as low as possible. ExplorerZ's recommendation of 1/30s should be good. (This applies to shooting with film also.) If shutter speed is equal or higher than the refrech rates, you will see horizontal lines or partial screen. If using camera phones or the like, try using night mode.
No circular polarisers! They do not work with LCD like Frenchbean mentioned.