Wash the headlights with soap and water
Dry the headlights completely
Mask off the paint around the headlights
Clean the lens with rubbing alcohol
Wet-sand the lens with 1000-grit sandpaper
Wet-sand the lens with 2000-grit sandpaper
Wet-sand the lens with 3000-grit sandpaper
Rinse and dry the lens
Apply a headlight polishing compound
Buff the lens with a microfiber cloth
Apply a UV-protective sealant or clear coat
Let the sealant cure fully
Replace the headlight assembly if the lens is too damaged