While out on vacation to the east coast of Canada to visit my family, I decided it was time to bring some life back into my sisters Mystique's headlights (And to test this on her car first

). I did this at the end of a lot of driving as evidenced by the amount of bugs on the front of the vehicle. Figured I would share the process as many Contiques suffer from this syndrome:
Before:
Before driver's side:
After passengers side
Halfway both:
The lights look just like new - pictures do not do it justice. Unfortunately, I did not get a chance to get a picture after I was done both of them and washing the car.
Pretty simple process that I have been using for years to do the dashes and plastic lens' on classic cars:
Step 1: Clean the lights
Step 2: Mask around the lights with masking tape
Step 3: Start off with 1000 grit wet/dry sandpaper (yes.. sandpaper). Wet down the lights before you begin. Sand away using inline motions across the light. Have a garden hose handy to keep the surface wet, and to wash away the water that builds up with dirt etc from the lights. Always make sure the surface is is wet. You may have to use 400/600 grit if there is excessive discoloration and pitting.
Step 4: Follow up with 1500 grit paper until most of the scratches etc are gone, as well as the yellow haze that has built up over the years.
Step 5: Dry off the lights - Grab a "beverage of choice" before you look at them. The lights will look horrible after the previous step. You will barely be able to see the actual bulbs etc.
You may have to re-apply masking tape.
Step 6 (Optional): Use Meguiars's metal polish to bring the lights back to life once again. This polish is more aggressive than the stuff in the nest step, so it saves a bit of time. Use firm circular motions - This requires lots of elbow grease. Once you are satisfied, polish with a clean cloth.
Step 6: Apply 3M plastic polish to the lights, and apply similar to the last step. Keep applying until satisfied with the finish (Assuming the lights are not too far gone). Use dry clean cloths to polish to a brilliant shine

.
Step 6: Grab another "beverage of choice" - you earned it.
Materials:
-Making Tape
-Package of assorted wet/dry sandpaper (400/600/1000/1500 grits). May have to buy separately.
-Source of clean water - bucket, hose etc.
-Meguiars metal polish
-3M Plastic Polish (Meguiars plastic polish should work as well).
-Bag of polishing cloths
-"Beverage of choice" - several required
-Friend (to do the other light at the same time)