1. Stop every two hours and get out of the car.
2. Keep plenty of snacks and a variety of beverages close at hand. I like coca-cola, water, and gatorade... Oh and if you don't have anything in the car that appeals to your taste buds you are allowed to buy things at the gas station, like giant 3 musketeers, slurpees, corn nuts etc. 
3. Mentos are the perfect road trip mint. You can only chew so much gum before your jaw hurts. Mentos give that refreshing mint sensation without the boringness of a mint... and they also come in the fun pomme vert flavor!
4. Make your playlist beforehand. You should not have to fiddle with your mp3 player while driving... Better yet make a cd... Then if you don't like the song all you have to do is hit one button on your dash that your hand can find without you even looking... Sing out loud!