Headlights on most modern vehicles are made of polycarbonate plastic, which is much more resistant to rock chips and cracks than glass headlights. The problem is that after a few years of being exposed to UV rays and other environmental elements, the outer surface becomes frosted, which blocks the light emitted by the headlight, making driving at night difficult and dangerous. Replacing headlights can cost hundreds or even thousands of dollars. Cleaning the frosted headlights so that they look like new takes some elbow grease and about an hour, but they can be made to look like new.
Place masking tape around the headlights, along the edges of the painted surface, to protect it from the sandpaper. Use several layers of automotive masking tape, since it won't harm the paint.
Wipe the headlights with polishing compound and a microfiber cloth to remove dirt or other surface contaminants. Move the cloth in small circular motions. It should take at least 10 minutes to completely cover each headlight. Rub the headlights until they look slightly dull.
Sand the surface of the headlights using 1,000-grit sandpaper soaked in water. Sand in the same direction, up-and-down from the hood towards the bumper, and never across. Keep the sandpaper soaking wet the entire time it touches the surface of the headlight to prevent grains of sand or dirt from scratching the surface of the headlight. Rinse the headlight and dry it to check your progress.
Repeat the sanding process using 1,500-, 2,000-, 2,500- and then 3,000-grit sandpaper and water. This process is necessary and cannot be left out, or the headlights will look more dull than they did at the beginning. Rinse the headlights completely and allow them to dry.
Wipe the headlights once again with polishing compound and a clean microfiber cloth. Once the entire headlight has been polished, it should look bright, clear and new.
The headlight can be wiped with headlight protectant polish found at most automotive stores, or it can be waxed to provide further protection from environmental issues. Don't forget to reapply new masking tape if the existing tape becomes torn, ripped or frayed.