You really don't need a buddy IN your Jeep, unless its a really experienced off-roader who can suggest lines of approach to you on difficult terrain. What you REALLY need is another 4x4 vehicle going with you, so you can pull each other out if you get stuck. Tow hooks on each end, tow strap (with nylon loops on the ends, not metal hooks), and air down the tires. You'll need to air them up when getting back on the pavement. Air them down to 10-15 psi for off road. If all you have is one of those cheap cigarette-lighter-plug air compressors, it will take a while to air the tires back up to recommended pressure. So, if there's a gas station not too far from the trail head, you can air them up to about 20 psi, and then drive SLOWLY (under 40 mph) to the gas station to fill them up to the recommended street pressure.

Oh yeah, in addition to leaving your travel plans with a friend or relative, take a map. In fact, it wouldn't hurt to get two maps. Take one with you, and then mark your travel route on the other map and give it to the friend or relative.

If you're going in snow country, take really warm clothes and boots, even if you don't plan to wear then while driving. You'll really need them if you get out of the vehicle for very long trying to get unstuck or walking your way out.

If you're on a relatively mild state park trail, that's a good place to learn about driving and about the quirks of your vehicle. As you progress in experience, you can try more difficult trails -- do this gradually. At some point, your ability will exceed that of the vehicle, and that's when you'll start considering emptying your bank account for modifications! (g)

The most important thing is: HAVE FUN and TAKE PICTURES!