Wash the headlights with soap and water
Dry the headlights completely
Mask off the paint around the headlights with tape
Wet-sand the lens with 1000-grit sandpaper
Wet-sand again with 1500-grit sandpaper
Wet-sand again with 2000-grit sandpaper
Rinse and dry the headlights
Apply a plastic polish with a microfiber cloth
Buff the headlights until clear
Apply a UV sealant or headlight protection coating
Reapply protection regularly