How do I clean up a camera lens or a lens filter?

There is a solution come with the kit that enables you to clean the lens.

Don't ever think of cleaning the lens with alcohol or using some kind of glassware cleaner, they will destroy the coating layer on your lens, which will result in bad quality of picture.

Always Try to cover your lens with a filter, when it is dirty, just clean the filter, don't do many things with the lens, because it is risky.

They sell lens cleaning kits. Use the lens solution (usually isopropanol soln) and cloth to clean the camera lens. Don't use the isopropanol soln to clean a filter. This can remove the UV or other coating. Use water only to clean a filter.