Fog, driving, and off-road lights: Common to off-road packages, factory-fitted lights come with two caveats: Lamp height and brightness rules vary by state (for example, use of roof-mounted operating lights may be illegal on the highway). And factory lights rarely have the optical performance of those offered by specialists like Hella and PIAA. However, before you invest in aftermarket lights, verify that your existing units are properly aimed, as factory headlamps and auxiliary lights are notoriously out of alignment, and a simple adjustment may give you the additional illumination you need.

Rock rails: Body reinforcements or protective steel tubes that run at the lower edge of the body between the tires, rock rails are standard only on the Jeep Wrangler Rubicon, but may be added to other vehicles. Before you invest in rails, ask yourself a few questions: Will the terrain you'll be driving be rocky enough to justify the extra weight? Are the units really rock rails or merely side steps in disguise? Can they carry at least half the weight of the truck? Do they reduce ground clearance below the doors? Do they carry a guarantee for performance?

Wheels and tires: Despite street trends, wider wheels and lower-profile tires are not beneficial off the road. The largest factory tire offered on an off-road vehicle normally works best. A more aggressive tread and a tall, flexible sidewall will generally get you further into the wilderness than pavement-biased rubber and provide the most comfortable ride at the expense of ultimate street handling. Avoid a wheel that has the metal tire valve stem sticking out, as it could get caught on mud, ice, rocks, or buried tree branches. Note also that tires rated for both mud and snow rarely excel at both, and the rating doesn't apply if there's no pavement below the mud or snow.

Other equipment that will have a bearing on off-highway ability may be factory options or available through the dealer from manufacturer special-parts divisions (Chrysler's Mopar, GM Performance Parts, and Land Rover Kit, for example). A common addition to many modern 4WDs is running boards or side steps, so you can get your trousers dirty more easily. If you opt for them, make sure they can be removed quickly and easily, such as the Hummer H2's. Although steps are helpful for ease of ingress and egress, they're far more hindrance than help on the trail. Powered units found on some lux SUVs are even less desirable on the trail due to their length and ground clearance.

Some companies offer an optional winch (standard on the Dodge Power Wagon). If it's highly probable that you'll be stuck alone somewhere off road at some point, a winch may be helpful. If not, it's just more weight and complexity. Factory winches have been tested to assure airbag compliance and may be warrantied with the vehicle. Winches are rated in single-line pulling power, usually with one wrap of cable on their drum, and are most effective if rated for approximately twice the weight of the truck (a 6,000-pound truck should have a 12,000-pound winch). Be sure to ask about installation costs, accessory kits, and instructions on proper use, so you don't injure yourself or someone else when you use it.