What's the single best way to keep your LCD screen in pristine condition? Prevention. It may seem like common sense, but the majority of scratches and other damage aren't caused by dropping your camera into tiger traps. If the LCD screen doesn't come with a cover or fold-away feature, make sure you keep it in a clean, non-abrasive case when not in use. Even when put away, try not to put too much pressure on it: LCDs are fragile, being made of plastic and not glass, and even a little pressure can cause permanent damage. Try to adjust your grip on the camera so that your fingers avoid touching the screen while adjusting settings on nearby buttons, as smudging from fingerprints is difficult to remove.
Also, make sure you gently clean the screen with a lens or other microfiber cloth on a regular basis. Cleaning solutions can be bought fairly cheaply at any electronics store, or you can make your own 50/50 mixture of distilled water and isopropyl alcohol. Be sure not to use ammonia-based cleaners such as Windex! Make sure the LCD screen is off when you do so.
Do not leave water on the screen itself after you are done, as that could cause damage. The best way to ensure that there is not excess liquid left on the screen is to dampen the cleaning cloth with the cleaning solution, as opposed to spraying the screen and then using the cloth.
and make sure there is no liquid remaining on the screen when you are done