Camera lenses should be kept clean, but it is a mistake to clean them too often. The marginal improvement in picture quality is not worth the risk of lens damage.
A camelhair brush is a soft brush and reduces risks of scrapes to your lenses. You will also need photographic lens tissue. Do not use eyeglass tissues; they are impregnated with chemicals that will damage the lens. Lens cleaning fluid will also come in handy for the cleaning process.
When you clean a lens, start by blowing or brushing away loose dirt. Never touch a lens surface with anything other than a clean lens tissue or lens brush, and never try to dismantle a lens in order to clean an inner element. Should an interior lens surface become fogged, take the camera to a repair shop. You can check a lens for fogging by shining a flashlight beam through the back of the lens.
Use a clean camel hair's brush to whisk dust from surface of lens. If lens is removable, take it off the camera and brush rear lens surface as well as the front. Be careful not to rub sand or grit across the lens. Use an ear syringe to blow away any remaining dust and dirt, especially particles that might be caught at the edges. Another safe method is to breathe on the lens and use some lens tissue to wipe off any debris.
Tear a piece of lens tissue in two, roll one half into a small cylinder, and dry off the lens by gently brushing it's surface with the frayed end of the tissue. Move the tissue in a swirling motion. Never use a lens tissue more than once. To do so can cause dirt to be re-applied back on the lens and cause scratching.
If the lens is still dirty and it's hard to remove the dirt, repeat this procedure over again until the lens is completely clean. Never place your fingers on the lenses when taking pictures. This will require you to clean your lenses every time you use your camera. Doing this will also reduce the life of your camera and your lenses.