The first rule is to clean the lens only when necessary! A little dust on the lens won’t affect the image, so don’t be compulsive. When needed, use a soft brush, such as a sable artist’s brush, and a blower (an ear syringe makes a good one) to remove dust. Fingerprints can be very harmful to the lens coating and should be removed as soon as possible. Keep the lens covered when not in use to reduce the amount of cleaning required.
Clean a lens by first by using a brush or blower to remove abrasive dust particles. Then use a lens cleaning cloth (or roll up a piece of photographic lens cleaning tissue and tear the end off to leave a brush like surface). Put a small drop of lens cleaning flluid on the end of the tissue. (Your condensed breath on the lens also works well.) Never put cleaning fluid directly on the lens, it might run between the lens elements. Using a circular motion, clean the lens surface with the tissue, then use the cloth of a tissue rolled and torn the same way to dry. Never reuse tissues and don’t press hard when cleaning because the front element of the lens is covered with a realtively delicate lens coating.