Excerpt from Scott Kelby's Digital Photography book, Chapter 3, The Truth About Lenses—Cleaning Lenses
As soon as dust, debris, grease, or dirt gets on the lens, disaster is waiting to happen. Every photograph you take with that lens from then on will show the dirt, grease, or dust. Every photograph. All of them!
That is why it is important to clean your lenses before you head out, and of course whenever something gets on the lens. You can usually remove the dirt with a special lens cloth. It is best, however, to blow as much debris as possible off the lens first. Simply blow it away with your mouth or, better yet, use a small blower that produces a puff of air when you squeeze its bulb.
Once all visible dust and debris are gone, gently wipe the lens with the cloth in a circular motion. For about €20, you can buy a cleaning kit with a blower, a cloth, and a very useful lens pen with a fine brush at one end and a special cleaning tip at the other. A kit like that works wonders!
Long Lenses Usually Have a Tripod Collar
A long lens usually comes with a special collar for mounting it on a monopod. That collar also offers an unexpected convenience. Loosen the locking knob and you can rotate the camera a quarter turn while the lens stays in place. This lets you switch from portrait to landscape orientation in two seconds.
