What's the best lens cleaner for my DSLR camera?

I stick with the gentlest thing that actually lifts oil.

Look for an optics-safe liquid that is water based and pH neutral, and free from ammonia and fragrances.

A tiny drop on a clean, lint free wipe, then a light spiral from center to edge, does the job without streaks.

Let it evaporate on its own and resist scrubbing.

If there is grit, remove it without touching the glass before using any liquid.

Works fine.

Start with a gentle air blower to lift loose dust so you do not grind grit into the glass and then wipe with a lightly dampened microfiber cloth using light circular strokes from the center outward... Skipping the blower can leave tiny scratches, so be gentle and avoid pressing hard.