I used 91% Isopropyl Alcohol to clean the greasy finger prints nothing happened to the screen.

spitting on the screen and wiping it off with the tshirt?

I use Zeiss Lens Cloth, Pre Moistened...Works like a charm, and will do no damage

using water isnt good?

Water is fine...but water will not help remove oils such as finger prints.

Geez, cant you just get a soft napkin and some tap water? That does it all the time.

lick it... then wipe it with a tissue paper

Use the cloth that came in the box like this:

clean with the bottom side (that doesn't have the Nokia logo on it). Also clean from left to right in broad swipes with your whole palm laying on the cloth flat against the screen as opposed to going in circular motions.

I was surprised that with above technique after 2-3 swipes the screen gets flawlessly clean.

I use a diluted vinegar solution for household cleaning. Very roughly 1/3 of store-bought vinegar and the rest water, For notebook and cell-phone screens, I soak and wring out a microfiber cloth towel (nothing fancy, the kind sold for use in cleaning cars), and spritz it with this vinegar solution. Wipe once or twice, form a point and get the edge, very light pressure, and then turn over the cloth, final wipe. The water evaporates in a few seconds, no need to blow on it.

Hello:

You might want to consider using distilled water and a lens cloth. For eye glasses and LCD monitors/TVs this has been better for me than any chemical solution.