With all this talk about digital camera lenses, we cannot forget that such expensive equipment deserves expert care. Lenses that are well cared for will not only continue to take higher quality shots, they can last for years. Start by using a microfiber lens cloth to remove dirt and dust from the lens itself. Use gentle strokes working towards the outside of the lens. Stuck on dirt will require cleaning solutions, but only use those dedicated for lens cleaning. Household cleaners can easily damage it. While cleaning is important, there is such a thing as over-cleaning. Too much cleaning can scratch the glass and remove essential surface coatings.
Scratches are the worst thing that can happen to your lens. You can't really repair them yourself --just take precautions to prevent them such as using a filter. While many filters can add cool effects to your photographs, they can double as a protective layer along with your lens cap. Water is another mortal enemy of the lens. Water can not only damage the electronic circuits in the lens, it can get inside the internal lens and dry, leaving water spots you cannot get rid of. When shooting out in the rain or snow, use a rain hood to protect your camera.
To protect the lenses when not in use, it's imperative to utilize lens bags and cases or camera bags with plenty of cushioning. Sturdy, well-made bags will prevent shocks and damage. Consider using a few silica gel packets in the bag to protect your equipment from collecting moisture.