The Eclipse Lens/Sensor cleaning fluid comes recommended by all professional photography websites, and it's not hard to see why. I had gathered a small collection of lenses and had always postponed cleaning them due to a combination of fear of damage, laziness, and apathy. After a day in the rain, one of my lenses really started to get dirty, and I finally bit the bullet and bought this cleaning fluid as well as a set of 100 pec-pads (also available on Amazon).
I wish I'd done it sooner. This stuff is really easy to use. You simply dab a few drops on to a pec-pad, and wipe in circular motions, starting from the inside of the lens and working your way out. As soon as you wipe, the fluid evaporates, leaving no streaks or smudges at all, and making your lens or filter look good as new.
Definitely buy this stuff now, and never worry about finger prints, dust, mould, or smudges ever again.