I had a shoot out on the Island a couple of days ago and watched someone ruin his nice camera. It happened so fast I was unable to stop him.
It was windy and sand was blowing around so he decided to clean some sand off the front of his lens with his shirt (which was also sandy). All he succeeded in doing was grinding very nice scratches into his glass. Within about 5 seconds a nice lens was turned into a paper weight.
What did we learn from this?
1. Always use a UV filter on your lens if you are in a harsh environment like the beach. The cheap filter will get sandblasted instead of the expensive lens.
2. Never use a kleenex or paper towel to clean your lens. These are rough paper and could easily scratch your lens, even without the sand and grit helping.
3. Only use a proper lens cleaning kit. Blow off dirt, gently brush the remainder away, then use the solution and lens cleaning cloth.