1. Make sure your drivetrain is in good working order, including the mandatory low range. Whether with an automatic or a manual transmission, you must have confidence that you won't pop out of gear under load either up or downhill.
   
2. Make sure the brakes are in good working order. Your brakes are vital and, if something in the driveline breaks, are the only thing between you and catastrophe. With an automatic, brakes are used much more on steep descents than with a manual.
3. Uphill sections can be run in Drive or Second it's a mild uphill, but if it's steep and slow, shift to First to keep the tranny cooler, run the fan faster and allow slow speeds to maintain maximum control. If you're going slowly enough, it will do this on its own, but mine tends to shift into Second, so I just pull it down to First. Higher gears slip the torque converter more and raise temps. Manual transmission guys will figure their gear out by default (bogging/stalling or high revving will determine that.)
4. If you constantly use the brakes to maintain low speeds on milder downhill sections, you're in too high a gear. Shift down and let the engine control your speed. The only complaint I have with automatics in FSJs is that First gear low range won't keep you slow enough if it's steep. Brakes must be used constanly here, and they usually don't heat up at that low a speed, but if you can feel them fading or getting spongy, do not proceed. Let 'em cool off for a while, and err on the side of a longer rather than shorter.
5. If you do lose brakes, jump on the parking brake, but if the rear linings and drums are overheated they won't help. It's better to scrape the truck on the side of the mountain to scrub off speed than to fly off a cliff. Depending on the terrain, this may not be an option, as it may not be a nice rock wall, and the slope could cause a rollover, but if it's steep enough and you aren't lifted, your front tires may just slide sideways and help to slow you. Never shut the engine off. It won't slow you down with an auto and will eliminate power steering, vacuum from your power brakes and may lock the steering column. All bad things.
6. Know your vehicle and it's capability to do the selected trail. It's good to address vapor-locking and stalling issues before going to higher elevations, but sometimes that's not practical, as you can't tune for 12,000 feet at 2,000 feet. Be prepared if those problems crop up on the mountain. Know where your pumpkins and spring bolts are in relation to the rock you're about to drive over. That last one is more important to stock rigs, of course.
7. Know your own driving skills and capability. If your'e a novice then stick with the easy trails and work your way up. Veterans can give you advice and spot you, so it's good to be accompanied by a few.
8. Know the selected trail, if you don't then find out from books, or other off roaders that have done the trails to identify any problem spots or if you should even be driving that trail. Avoid wheeling alone if possible. You never know what might happen or how long you may be there, hurt, cold, or broke down. Take some tools and survival supplies.
9. Always wear your seat belts. The chances of surviving are much greater if you remain in the vehicle. But make sure your gear (jack, toolbox, chain, etc.) is tied down. A hydraulic jack in the noggin could end your FSJ days.
10. Stop often and enjoy the incredible view, a snack, a story, take some pictures and maybe smoke a cigar.
    

Ken Hanawalt