Depends on what has been done recently. I would start with changing the plugs, transmission fluid, transfer case fluid, differential (s) fluids, coolant fluid, power steering, brake fluid, engine oil, rotors/brake pads (emergency too), belts, hoses, shocks, stuts, and cabin air filter. Put your rig on a lift and check for any play in the wheel hubs. Inspect your steering rack, bushings, and exhaust system. While your under the rig, lube the chassis and inspect for any obvious fluid leaks.