Front sway bar links (easy 30 buck fix)
Torn CV axle boots
Front driveshaft (lay on your back, grab it and shake. Should very little to no movement in any direction. (Not a cheap fix, close to 300 for the driveshaft, if the problem is in the diff much more $$)
Rear driveshaft (same)
Crawl under it looking for leaks at the transfercase/tranmission and output shafts
Look for leaking pinion seals on front and rear differentials
Run your hand across the tread surface of all 4 tires, feel for cupped or un-even wear, beware of brand new tires, they could have bought them to mask other serious problems
Take it for a drive, listen to what the truck tells you. Humming, grinding, popping, snapping noises should be non-existant. It should drive straight and true with no vibrations. Try every option available, the electric seats, tilt wheel, lumbar support, Smoothness of the shifter, OD shuts off, when you start it it fires right up. Turn the wheels all the way to one direction and drive it slowly in a circle, it should not hop or make any noises. If it hops it could be a transfercase issue, popping/snapping noises are most likely the CV's.
Try all the electric windows, electric locks and electric mirrors. Manually lock each door and try to unlock it with the keyfob.
Try to open the rear doors from inside the truck
Look for evidence of rot under/behind those pretty running boards (Very common spot)
Look for rot around the rear wheel wells, the "dogleg" at the rear door, and all 4 door sills.
Check the rear hatch for rot along the bottom edge inside and out side the truck, also the hatch cylinders
Open the hood, the hood cylinders should hold it up. Check the back side of the radiator, area around the waterpump for evidence of leaks, look at the gooseneck where the thermostat is for leaks, check power steering lines for evidence of leaks, open the air cleaner (this will only let you know if they are being truthful about always taking care of it), look at the valve covers for leaking around them, with the engine running listen to the alternator for weird sounding bearings
When you have the front wheel turned in one direction, you can lift the flimsy black "skirt" in the wheel well to get a look at the side of the block and what the wires look like. Take a wire off and look at the spark plug, how old does it appear to be?
Look under the seats, in the back under the mat, look everywhere for evidence that the truck was a travelling trash-bin that was just recently cleaned up to look cherry.
Look up on the headliner, some owners have reported a small leak around the sunroof, it will stain the headliner a little brown and may cause the fabric to peel away from the backer.
Check the function of the rear view mirror, (if it has a slide switch on the lower front of it) supposed to control the length of time the headlights stay on once you exit the truck and also be "self dimming" (IE: not night time setting)
I think that just about covers it
