Fixing Jeep Death Wobble

Many have experienced it in a Jeep. Although it's more common on lifted Jeeps, it can happen on any coil sprung solid axle setup.

Death Wobble - a quick (4–10 Hz) oscillation of primarily just the steerable wheel(s) of a vehicle. Initially, the rest of the vehicle remains mostly unaffected, until translated into a vehicle yaw oscillation of increasing amplitude producing loss of control.
Coil-sprung vehicles with a track bar setup such as the Jeep WJ, XJ, ZJ, TJ, and JK with both stock and after-market suspension lifts often have this problem.
This video outlines (in my opinion) the best first step to solving death wobble.