I clean all my LCD screens each weekend with a mixture of 1 part isopropyl alcohol to 1 part filtered water. I normally use a smooth microfiber cloth, but in a pinch, facial tissue will do, but make sure it's totally saturated and squeeze it as dry as possible.
When wiping the screen, don't exert pressure. Simply pull the cloth or tissue around the screen, and use your free hand to fan the screen. The liquid will dry away immediately. Look at the screen from different angles and if you see spots, run the cloth over the area a few times to soak the spot and it will come off. Don't press down and try to rub out the spot or you might scratch the screen if there is some sort of debris or deposit (like a cookie crumb, or a dead bug).
Also, look at the cloth or tissue as often as you can between wiping. try to turn or fold it so you can wipe with a clean area of the cloth.
You can use isopropyl alcohol undiluted to clean the screen, but it dries instantly and leaves a lot of streaks. Just thought I'd mention that in case you don't have filtered or distilled water handy
If you buy pre-moistened computer screen wipes, make sure that it says it's safe for LCD screens. If it's only made for traditional CRT screens, it most likely contains chemicals that can make your LCD screen dry out, causing it to look cloudy, and even crack over a period of time.
You can search Google for more information on what's safe to use on LCD screens