Skid plates under the engine oil pan, and transmission oil pan if auto. They need protection, the tranny more so as there is a solenoid directly under the pan magnet which eliminates clearance. Cracked solenoids are common.
Steel rims and high aspect ratio tires - alloys are known to be damaged easily on rocks and curbs, low profile tires have less sidewall and impacts distort the tires over more of the short sidewall causing even more damage. You can often beat out a steel rim, but a cracked alloy is toast.
Mud and snow rated treads for more traction, if an all terrain is chosen, read up on the ratings on Tire Rack for the best recommendation for the dollar. Things have changed and the old school treads from ten years ago are sliding to the bottom of the list.
If you do change the overall diameter of the mounted tire and rim expect that the speedo will be off, there are electronic correctors to get it back. They are necessary because the ECU does read that when choosing the fuel injection map.
Tie down or eliminate anything loose in the car, as the 4WD guys have learned. They might deliberately flip theirs over on the roll bars, but regardless of whether you meant to or not, things like toolboxes, Thermos jugs, and you don't mix well when for some reason the car is tumbling downhill out of control. No, we don't intend to do that. Yes, it happens on bad back roads all the time.