Worn cotton t-shirts work best. Launder without fabric softener or dryer sheets.
With plastic lenses, don't use paper products, including Kleenex, toilet paper, napkins, or paper towels. Paper (wood) fibers are hard enough to put microscopic scratches in lenses or coatings, eventually making them appear cloudy.
Microfiber cloth is pretty lousy for cleaning lenses, in my experience.