Summer is fast approaching, and with it comes the possibility of road trips. They can be great fun, and I highly recommend one. My wife and I are leaving on our own tonight. A bit of preparation and forethought can keep the from descending into utter chaos, as well.
Know your route. Pack a map, and know how to read it. GPS can fail, usually at the worst time. If possible, study your route before you leave. Check the availability of alternate routes as well. If it's a route and area you're not familiar with, start looking for fuel at half a tank. In many places I have traveled, it is entirely possible to be 100 miles from a gas station.
Carry extra snacks and drinks. You'll never regret it, especially when you need it.
Give your vehicle a checkup before you leave. Check your fluids and top off any that are low. Check your tires for wear and for proper inflation. If you're nearing any regular maintenance, get it done before you set out. Have any repairs you've been putting off done as well. If you don't know how to do any of these checks, many mechanics will perform them for you for a nominal fee, if not for free.
Get out there, see something interesting, and have the time of your life. Plan ahead, and don't let anything ruin your time.