LWM

First and foremost, before you hit the road, you need to make sure your 4WD vehicle is in sound mechanical condition.

To determine whether your 4x4 vehicle is trail ready and capable of surviving a trip off-road, first do a visual inspection - inside and out. Then, take a few minutes to more closely inspect the inner workings of your ride - make sure that the following parts are in good working condition and you don't hear any strange noises coming from these areas:

Axles & Differentials - hubs, seals, vacuum lines, shift motors, vent lines, front u-joints
Battery - clean terminals, check for damaged or corroded wiring
Brakes - drums, rotors, pads/shoes, fluid, hoses, leaks, check e-brake, brake lights
Belts & Hoses - look for cracks or bulges
Body/Frame - look for cracks
Cooling/Heating system - look for leaks, fluid levels, clean and repair fins, check hoses, thermostat, radiator cap
Driveline/Transmission - inspect case and shifter, leaks, fluids, universal & cv joints, skid plates
Engine - carburetor, fuel injectors, spark plugs, wires, pcv valve, pumps, spark plugs, distributor & wires, belts; check for leaks and cracks
Exhaust - muffler, tailpipes
Fluids - oil, transmission, brake, radiator coolant, gear oils, wipers, power steering
Lights - headlights, brake lights, auxiliary lights; make sure they're aimed properly
Nuts & Bolts - tighten axle u-bolts, lug bolts, nuts
Steering - check alignment, fluid level, belts and hoses, pump and reservoir for leaks
Suspension - springs, shocks, alignment, wheel bearings, steering linkage
Tires - tighten lug nuts, air pressure, tread wear (including your full-size spare), look for cuts and missing chunks
Wipers - check for wear, fluid level

More information here!