A note on Death Valley trails: the conditions of most of the Death Valley trails are extremely dependent on weather conditions in the previous few weeks. The trails get re-graded and improved, but are very susceptible to flash floods and wash outs. In particular the canyon trails can be deadly if you are caught in a flash flood.
Easy: Can be done by the novice. Many sections may not require 4WD in good conditions. Roads are unpaved, infrequently maintained and are likely to have moderate grades, potholes, ruts, and edges with no guard rails.
Moderate: Can be done by the novice. Most people will find these trails to be a fun adventure with some steep climbs, narrow ledge roads (plenty wide for one Jeep, but not wide enough to pass in many places), some rocks that require slow & careful ascent, and water crossings that could be as high as the bumpers. The key is to take your time, go slow, and pay attention. The biggest concern on these trails is watching for other vehicles and taking the time to find a safe place to pass.
Challenging: Not recommended for the novice. Even experienced 4-wheelers may find the obstacles and ledges intimidating, and damage to vehicle is possible, unless extreme caution, careful throttle control and precise wheel placement is exercised.
Difficult: Experienced 4-wheelers only. Solo travel not recommended. Vehicle damage possible, even with slow ascent and careful wheel placement. Tippy sections, rocks and ledges 16