My best advice: DON'T!!

A lens can have an amazing amount of crap on its surfaces with NO apparent effect on the quality of the image. Every attempt - EVERY attempt - at cleaning will have a detrimental effect on the surface of the lens - the first to be damaged will be the coating, then the glass itself.

The saddest sight in all of photography is to me the once beautiful Leica or Hasselbled lens with a large translucent spot in the center of the firrst element, the result of "knee-jerk" cleaning.

Keep a "plain" (Skylight, UV, etc,) filter on the lens. Then, if you MUST clean anything, every time (read: anally) you can watch the translucent spot grow on the filter, and know you have preserved your "good" glass.

IF I decide that there is no other alternative - every year or two, or three -and I MUST clean the lens itself, I will use clean water, and surgical cotton, being careful to use as little pressure (read: awfully close to "none") as possible.