How to clean LCD screens

From laptop to desktop to smartphones, if it has an LCD screen it will get dirty at some point and even more so if it has touch capability, so how do you get them clean again?

The DO NOTs:

1. Do not use any form of alcohol to clean the screen
2. Do not use chemicals such as Windex or ammonia based solvents
3. Do not spray any liquids on the screen unless it lying flat (you can use commercial LCD cleaners)
4. Do not wash the screen
5. Do not use laundry detergents on the screens
6. Some hard polyester based cloths should be avoided (they can actually help in damaging the surface of the screen)
7. If there is a visible layer/film of dust on the screen DO NOT use a dry cloth to wipe it away (the cloth must be dampened to enable it to "trap" the dust) 

The DOs:

1. Use a dampened piece of lint-free cloth (cotton-based is best) and wipe the screen. Be careful to not use too much force.
2. If you must use a tiny bit of mild soap (hand-soap), place the screen flat and even then use a dampened cloth (not wet) and avoid any liquid getting under the bezel of the screen.

NB:  If there are children in the house try and discourage eating at the computer or using the computer with soiled hands.