I always use a yellow duster and nothing else. Make sure it's clean and hasn't been used for anything else, like polishing the furniture.
I always find introducing liquid leaves streaks.
A gentle, yet firm and persistent wipe with a yellow duster gets any marks left on my screen (also a VT30) off. I occasionally breathe on the screen to introduce a hint of moisture, if there is a particularly stubborn mark to remove.
a micro fiber cloth or better still an eye glass cleaning cloth with eye glass cleaning fluid instead of any other complex fluids. Remember to move the cloth in one direction only. As a cloth a really gentle cotton napkin can be used, just be sure it has no smelly or cleaning add-ons or stamped colors. If it cleans your eye glass and does no harm to its coating it will do no harm to the plasma coating either.
On the cheaper side you can use the regular house windows cleaning spray, but you will not benefit from anti-static element, as they have none
You need to use a barely damp micro fibre and buff with a dry micro fibre before the water drys.
May get better results if you clean half the screen as above then the other half
I use cooled boiled water from the kettle comes up perfect everytime even removes slobber from my 2 boxers.
If using kettle water make sure you dont use the dregs from the bottom as limescale will scratch the screen/coating.
If you want to just do a spot clean breath on the area and quickly buff with a dry microfibre.
A few months ago got a phone call from my mate asking if I knew how to get Brasso off his G20 screen,told him to leave it and I would be straight over.When I got there it was Brasso gadget cleaner that could be used on tv screens and not the metal polish,this stuff just left an oily mess all over the screen.
Using 2 microfibre cloths cooled boiled water and working small areas at a time after about 15mins the screen came up like new.
Not sure if i should do but i use a couple of lint free cloths, one wet with water and fairy liquid (wrung before touching the screen obviously) to clean any marks or stains and then i use the other cloth to buff it aftawards to remove any streaks.
It works great interms of having a spotless clean and streak free screen.