Cleaning screens

What’s the best way to clean a smartphone or iPod screen? I keep one of those cloths for cleaning glasses in one of those uber-small Ziploc bags that pharmacies use for pills in my wallet. That’s fine for a slight cleaning, but is there a cleaner of some sort that works for this?

drop of water on a cloth or paper towel is usually fine
if you need something more substantial, a wetnap
if it’s really messy, rubbing alcohol (here is ethanol)
don’t worry, it doesn’t eat the coating