The easiest way to go down
1° Riding along, get closer to the edge, wheels parallel to the side drop.
2° When you feel ready, brake the front wheel for an endo slightly off-centered sideways.
3° Carry on lifting the rear wheel while at the same time moving it over the drop.
4° In one push-up on the bars, eject the front wheel away from the edge.
5° That sends you off the wall, pull the bike sideways to realign it under you...
6° In the air, extend your feet and let the rear wheel drop to reach ground first.
When the back wheel lands, damp the impact with your legs and arms so that when the front wheel touches, most of the impact is already absorbed. The front wheel shouldn't bang on the ground (a wrist breaker). See this move in this video or in slow-motion
In the air stabilise the bike aligned with your body, otherwise you're likely to be ejected sideways, on impact with the ground. Let the back wheel hit the ground first, with the rear brake "on" to gain extra damping power with the "bottom bracket-to-rear-hub" lever. (we 're talking hardcore physics there! Check out the lecture).
Use the spring of your legs to absorb most of the impact, then lowering naturally the font wheel to the ground by extending the arms. Here again, fat low pressure tyres are more comfortable. The next step is to drop off from a 180° turn on the front wheel.