To protect against lens flare you should fit a lens hood onto the end of your lens. Lens flare is something that may happen when your lens is pointed at a bright source of light. It can be caused by the internal reflection and refraction of light in the optical components of your camera lens. The sun may be too bright for the lens and it could easily ruin your photograph. When bright light shines on the lens, but not in the field of view, the flare produced is usually a haze that can wash out the camera's image and reduce its contrast.
To avoid this effect you need to shade the lens with a hood or by holding an object or your hand between the source of light and the lens. This will effectively cut out the flare.
You can also get coated lenses that have a thin layer of transparent substance on them to help reduce light reflection. If you are working in a studio you can attach a gobo to the lighting to help keep it from causing flare on the camera. Lens hoods can be bought for about $20.