What's the best way to clean a lens filter?
I bought a used lens that came with a filter. The lens is in great shape but the filter clearly has smudges and streaks across the front.
Am I better off buying a new filter?
What I do is get some lens cleaning fluid, put some on a lint free cloth and wipe the filter. Then I use a microfiber cloth to get any smears off. B&H has an extensive blog post showing how to clean a filter and lens with the tools you'll need.