A Citizens Band (CB) radio is not required but is highly desirable for group travel. Communication is important for safety and keeping the group together; you can be warned of road damage and can be aware of stalled vehicles. Furthermore, your trail leader will be telling those "with ears" what is going on at the front of the line and may share pleasant tidbits of local geology and history.
Bring all the emergency gear you can reasonably carry, including personal items like sun lotion. You know the rest... first aid, tow strap, fire-extinguisher, jack, spare tire, etc. for a comprehensive list, check our Offroad Suggested Tools and Parts List.
Make that tow strap the kind with loop ends; any hooks should already be secured to the vehicle. And remember, your registration fee doesn't include towing insurance, although we and other buddies often help when we can. The most experienced drivers have learned which parts are likely to fail on their vehicles, and they are often willing to make loans to the less fortunate.
Fill your tank, but few trails require extra fuel. The longest trip, the Hole in the Rock camping trip, may require fuel stops along the way. The longest day trip is Elephant Hill at 175 miles total, but only two others (Dome Plateau and Top of the World) come near to being 100 miles.
Do bring a suitable four-wheel-drive vehicle.

The term "jeep" in the event name should imply that we expect highclearance, off-road vehicles with twospeed transfer cases. Neither motorcycles nor ATV's are suitable, because their pace of travel is incompatible with the trucks, and it is impractical to include vehicles that are not legal for use on the paved roads. If your truck is showroom new, study the trail descriptions or talk to our experts. Some trails have many opportunities to tweak the paint and sheet metal, and you should be forewarned. Otherwise, stock vehicles should be capable of most 3-1/2 rated trails, but some of the newer, larger SUV's may want to choose a notch easier on the rating scale. Check on the trail specifics if you have long wheelbase, long overhangs, or fancy paint, and be wary if you have installed "rock-magnets" like driving lights or running boards.