I generally use RO but maybe once a month or so i spray glass cleaner on paper towels away from the tank and give the glass a real good cleaning. I think Frizt or something like that sells an aquarium safe glass cleaner.
I use glass cleaner on the rare occasion I actually clean it like thatbut I have a canopy covering the tank. If I didn't I don't know if I would. But for normal water spilling I just use a towel...