Your mantra should be "Slow and Easy". This will keep your rig from breaking or rolling over and will also keep our trails in better shape.
In rocky areas rocker panel protection should be considered mandatory. Rocker panels are easy to dent and expensive to repair.
Approaching at an angle can effectively increase departure angles and tame impassible cracks and ditches.
In deep sand use plenty of throttle to keep from sinking. Momentum is your friend. If you need to stop point your Jeep downhill or find some hardpack. Start smoothly to avoid digging in.
If you get stuck in sand, airing down your tires is often enough to free you.
Bring a buddy in his own rig. He can pull you out, get spare parts, spot the trail or keep you company while you make a repair.
Steep downhills - Do NOT mash your brakes, as this will almost certainly cause you to roll your vehicle. You may ease your brakes in very slightly but you should be letting the engine's compression be the braking factor. Use low range and low gear. Use the throttle to control your speed. If you slide, turn into the skid and again, do NOT mash your brakes.
Steep uphills - If you stall do not press the clutch. Instead use the starter while in gear to get you moving again.