Jack Nicholson had it right (of course he did) in As Good as It Gets when his character Melvin Udall has a bunch of different CDs made for their famous road trip in the convertible Saab. Music is key for a fun journey. This should be step one, as some research may be needed--mood, amount of songs you'll need to get you there and back, and subject (ex. The Mamas & the Papas if you're headed to San Francisco).
Map it out the day before. There's nothing worse than having all bags packed, front door open, and realizing you have no directions. This is even a good idea if you have a GPS, especially if you're going somewhere new. Using both Mapquest and Google Maps is fail-safe, to proof them against each other and check for any possible confusing parts or errors.
Choosing a good and clean stop along the way is best done before the trip begins--otherwise you may end up eating oatmeal for lunch in a Chinese-American diner where most of your fellow customers are surviving by oxygen tanks.
If the start time is early, coffee is a must. Either brew some of your favorite kind at home and thermos it, or make a pit stop at a reliable local place in the direction you're headed before the big trip really begins (for the Palm Springs to L.A. journey, Koffi is a great).
Bottles of water, granola bars, tissues, hand sanitizer (for post-gas pumping) are all great to have handy in the car, along with a fully charged cell phone of course.
Buckle up & enjoy the ride!
-- Leslie Anne Wiggins
Photo credit: Texaco / Jasperdo on flickr