Wash the headlights with car soap and water
Dry the area completely
Tape off the paint around the headlights
Apply toothpaste or a headlight cleaning compound to the lens
Rub the lens with a microfiber cloth in circular motions
Rinse the lens with clean water
Repeat if needed
For heavy oxidation, wet sand with fine-grit sandpaper
Polish the lens after sanding
Apply a UV sealant or clear coat to protect the headlights
Replace the headlight assembly if the lens is severely damaged