How do you protect your camera lens from accidental damage?
Rule #1: Always replace the lens cap when you are not taking picture.
Rule #2: If you are not going to take picture in the next 10 minutes, keep the camera inside the bag.
One common way to protect the lens is to attach a UV filter over it. When I bought my Canon 50mm f1.8 lens for RM300, I invested another RM60 for a UV filter. However, after comparing the pictures taken with and without the filter, I regretted.
UV filter degrades image quality. This is particular true if you use a low-quality filter. High-quality filters, such as those made by B+W, fare better, but they are pricey. As such, I suggest that you only buy a protective filter for the expensive lens. Never attach a low-quality UV filter to a high-grade lens.
Another way to protect the lens is to use the lens hood. Unlike UV filter, lens hood does not degrade image quality. However, hoods for wide-angle lenses may be too shallow to be effective.
Rule #3: Hang your camera over your neck, NOT shoulder.
If, on the other hand, you use a compact camera, remember to power it off when not taking picture.
Lens hood for protection