Lens manufacturers say that anything other than a microfiber cloth will damage the coatings on a lens. But microfiber cloths eventually pick up crap and they look like they're a pain to wash.
How do you keep your lenses clean? Are you using cloth/kleenex or microfiber cloths? If you use microfiber cloths, how do you clean those?
Just water and a regular dishtowel. If they're more dirty I'll use dishwasher soap. Rub it over with a finger to get the greesy stuff off and wash the soap off.
The microfiber cloth that usually comes with the glasses tend to stop working after a while, and I always have clean dishtowel anyway.
Outside my kitchen I use my t-shirt or if I'm wearing a shirt, I'll use the underwear top, because shirts generally aren't too good at it due to prints or fabrics. Yes I wear a "wife beater" under my shirt. It's what it's for, and I guess also for cleaning glasses.