Modern lens coating goes a long way toward protecting lenses from scratches, as well as reducing flare and intralens reflections.
A laundered 100% cotton T-shirt and some lens cleaning spray (available in most drug stores) will do an excellent job of cleaning lenses.
Camera repair author Thomas Tomosoy offers a simple method of cleaning lenses. It involves the use of plain white facial tissue - no scent, no lotion - and lens spray. It doesn't seem like this would make sense, but it works effectively. I've used this method to clean hundreds of lenses and have never had a problem.
You need to use extra care with older single-coated or uncoated lenses.
I've found the coating on some Leica lenses to be fragile and can be wiped away. The coating on Zeiss lens seems to be more durable.
If a lens is heavily soiled, I will use compressed air to first blow away any dirt or debris. Then I will clean the lens.
As long as you are careful, you should be able to clean your lenses without worry.
Wow! Lots of good advice and comments to dig into here. Iīm floored, thank you so very much! :-)
I use the Zeiss lens cleaning kit. It contains cleaning fluid, a micro fibre cloth, a (very good, very soft) brush and cleaning papers. It is rather expensive but I try to avoid cleaning my lenses to often (as Gerald said, you donīt do your lenses a favor by cleaning too often).