I have been amazed with the power of graphite. I use those Lens Pens (name brand, do not trust knock-offs). Here is my procedure. Use brush on pen to brush away dust particles (if necessary). Breathe on lens, twist cap of Lens Pen, open cap, and use the graphite pad to clean going in a circular motion from the outside inward. You can have a lens coated in finger oil and the graphite takes it right off without leaving cleaning marks or scratches. The pens need to be replaced after 100 normal uses or so. If anyone knows a better way to clean a lens (besides doing nothing at all), please let me know.

I also use methyl alcohol to clean glass (like quartz cuvettes), but never my optical lenses (the less liquids that could get inside the lens, the better). Also, I agree that UV filters for "protection" defeat the point in obtaining a quality lens.

Disclaimer: I do not work or have investments with Lens Pen or any of its subsidiaries, assuming there are any.