One of the biggest bang-for-the-buck improvements you can do on your car is to restore the headlights. I don’t know how many cars I pass on a daily basis that have cloudy, hazy, and yellowed headlight lenses, but I know that almost anyone can spend about $10-$15 for a do-it-yourself headlight restoration kit and can make their headlights look like new. 3M sells a kit, which comes with everything you need with the exception of a power drill to completely revitalize the headlights on your car.
If your headlights are foggy or hazy looking, it may be possible to polish them using something you might find laying around the house: toothpaste. Surprisingly, toothpaste can actually work quite well as a polish on headlights. Using toothpaste alone on the headlight lens can make a big difference in polishing the headlights, but polishing once more with a final polish like Meguiar’s PlastX can really make the restoration look complete.