Your choices for cleaning agents to use on LCD screens are very limited, because the coatings and/or glass that protect them range from breakable to downright weak. First off, always use a microfiber cloth (just like the ones used for cleaning eyeglasses), because some LCD screens are incredibly easy to scratch. Second, always clean them with the unit powered down, because it's easiest to see dirt, dust and smudges on the black background. Third, never rub or scrub the screen, because that can damage the pixels. And finally, always use a cleaner designed specifically for LCDs. Some manufacturers recommend that you use a small amount of cool tap water, or a 50-50 water/white vinegar solution. You'll find, however, that these can leave water spots and smears and, in my experience, dedicated LCD cleaning solutions like PixelClean or Klear Screen work a whole lot better.