"Restoring" your headlights
Sure, that rough yellowy mess on your headlights ruins their effectiveness, but paying big bucks for a "restoration kit" is total trash when you can DIY instead. Get a few sheets of very fine sandpaper from your local hardware store, soak them in water, and sand your headlights using finer and finer paper until it's perfectly smooth (if it's really bad, start with something like 400 grit, then progress to 800 and 2,000). Then use a polishing compound to make it shine, and you're back to being perfectly clear.
Opting for service contracts
If you've ever bought a new car, you've no doubt been bombarded with endless contracts and "warranties" that will see all of your maintenance taken care of, as well as damage to wheels and tires, etc. Newsflash: if these truly made financial sense for you to buy, they wouldn't be profitable for the dealership, and they would no longer be available. Think about that one...