Camera bodies and
lenses are pretty well sealed against dust and moisture. So you don't really ever have to clean the exteriors of your
camera equipment. On the other hand, if you don't want the dirt and crud that is on the camera body to work its way into your camera bag and from there onto an optical surface, it is worth wiping off the
camera body with a soft cloth. Slightly dampening the cloth with plain water certainly won't do any harm, though this wouldn't be
Basic tools for cleaning your lenses are canned air or a blower, lens cleaning fluid and a microfiber cloth. Try to blow dust from the lens using canned air or a blower. Using a fresh miracle
micro fiber cloth and wiping in a circular pattern will remove finger prints. Lens cleaning fluid will remove persistent dirt. Apply the fluid directly on the cloth, then use it to wipe the lens; don't put cleaning fluid directly onto your lens.
Certainly if you had the ability to safeguard your optics from every environmental source of dirt, there could still be filth accumulating on your camera optics as the plastics on your camera bag release gases. It is difficult to verify the claims of ROR', however the optics do visibly appear clearer after treating your optics with ROR and the $12.95 won't empty your bank.
If you must use an costly lens in a wet or dusty environment and want to refrain from obsessing over your optics, install a protective
UV filter on the front of the lens and plan on changing the filter every few years.