Are your tail lights old, dull, dim and dingy? Not too long ago I replaced the driver's side tail light lens and the shiny new one was a stark contrast to the original dingy one. The lights were very bright, but the passenger side was very dim. The insides of these light pick up road grime and diesel soot like crazy, especially the passenger side that's right above the tail pipe.
I thought about replacing the passenger side, but those things are expensive, $124 from a dealer, $50-$60 off eBay, but Europarts has them on special right now for $40, which is awesome. But, I decided to give it a go at cleaning the inside of the passenger side lens. Remove the bulb socket plate and the lens is held on with four nuts, easy to remove. Getting down inside the lens and cleaning it was a little tricky. I sprayed a lot of window cleaner (ammonia-fee, like Sprayway or Invisible Glass) and let it soak for a minute, then used a ½" wide paintbrush to get down in there and swirl it all around. Got it good and clean, then rinsed it out under hot water in the kitchen sink. Then, I poured an ounce or two of bleach into the clear lens section to clear up any yellowing and let it sit there for about half an hour. Rinsed that good, shook out nearly all of the water (you don't need to get it bone dry inside, it'll dry on its own very quickly) and then dried off the outside.
It's now bright and shiny just like the newer one is.
While I was at it I also did a little scraping and used some DeoxIT Red (D series 100% solution) contact cleaner on the bulb sockets (after the initial scraping cleaning, a drop or two of DeoxIT on a Q-Tip will do all of the contacts on one socket plate), and then coated them with DeoxIT Shield (can also use DeoxIT Gold) to protect them from any further corrosion and oxidation. Did the same thing to the bulbs. If you have intermittent problems with fast turn signals, which is usually an indication of either a burned out bulb or a poor circuit because of corrosion, cleaning the contacts will usually solve the problem if it's not a burned out bulb.
Take the same ½" paintbrush (when it's completely dry) and use a can of compressed air to clean out that little space between the steering column and the hazard flasher button. All manner of dust and crap will fall down into that space, dirtying up the contacts. Compresses air, a few swishes of the brush, more air, then, if you have it, some spray can DeoxIT (5% solution) down in there to clean it out and lubricate the contacts.