Old-fashioned cathode-ray tube TVs with flat screens had a thick glass plate in front of their screens, making them safe to clean with glass cleaner. Almost no modern TVs have glass covers, however, so you should never use commercial window cleaners, alcohol or ammonia, regardless of whether you have an LCD, LED or plasma television. Instead, stick to a soft, dry cloth, and dampen the cloth slightly if needed.
Most dust and debris comes off TV sets without requiring any liquid. Take a lint-free or microfiber cloth -- or an eyeglass cleaning cloth if your TV didn't include a cloth -- and wipe it softly along the surface of the screen. Don't push in on the screen: If you see the screen change colors under your hand, you're pressing too hard.
If dirt remains after wiping the screen with a dry cloth, unplug the television, lightly wet the cloth and wipe again. You only need a very small amount of water on the cloth to help remove stuck-on smudges, so your cloth should not be dripping wet, and you should never spray or pour water directly on the screen. Dry the screen completely before plugging the TV in. A few TV manufacturers, including LG and Toshiba, recommend against using any water on their screens, while others endorse adding a mild soap to the wet cloth if necessary, so check your TV's manual before cleaning to avoid breaking the warranty.