biketrials riding techniquesLanding on the front wheel
This is really a sophisticated move. The body weight shifting is a bit like in the roll-over climbing technique, jumping in full extension on the good pedal, and then throwing the shoulders forwards and pulling the bike with you. But on top of that, you must push on the handlebars to force the landing on the front wheel as soon as possible, and carry on rolling on the front wheel until the rear wheel has cleared the gap and has some grip on the obstacle.

1° Start like for a basic pedal hop, in balance on the rear wheel. 2° Lower the front wheel slightly, start kicking in the good pedal. 3° At the end of the pedal kick, throw your body forward.
4° Once in the air, shoulders above the bars, pull the bike with you by lifting the handlebars while extending the arms in front of you. Start aiming the front wheel at where you want to land. 5° Above the landing area, push the front wheel downwards. When landing the front wheel, use the brakes to slow the bike, but with inertia, keep your body moving by folding the knees. 6° By shifting your centre of gravity above the bars, move away from the gap. Then release progressively the front brakes and extend the arms to roll forward and finish off the gap.
See the move in a video
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same technique but climbing
How to practice?
Really, you should start practicing on a flat surface, with two lines as a virtual gap, or climbing up on a very small kerb. That way, you can learn how to throw your body forward and land directly on the front, without risking a bad crash on your face (that is if you miss the edge). Then try to release the front brake progressively to let roll the bike on the front, while the rear wheel is in the air. Vary the pressure in the brakes until you get this right. Only when the rear wheel has reached the edge of the obstacle, you can shift your weight back above the rear wheel. That will stop you rolling and stabilise the rear tire onto the obstacle.
In effect, the bike is used like a tilting bridge. It is just smoother than the typical rear pedal hop, with more control and fluidity (no blunt with the rear tire). If you land on a small area, and there is only room for one wheel, you can land and stay in balance on the front wheel, then release the brakes and hop to land on the rear wheel in a quick wheel-swap move, or turn on the front wheel while rolling, to position the rear tire on a nearby edge. At the beginning, it's easier to learn the move by climbing small kerbs on your wrong side (on the same side of your driving foot) video
When landing is safer
on the front than on the rear
At a Pro level: pushing the move further
Landing on the front wheel is another approach to big gaps. It makes the gap look smaller, and as you have some early front-wheel support on the obstacle it does not require as much pedal power as trying to land on the rear wheel. The overall move is really smooth, but missing the front-touch by only a few centimeters can result in a fully fledged face-plant onto the missed edge. So you really need a lot of confidence to cross these big gaps and land onto limited space.
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Full extension over the gap (Andrei).
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Cesar in ultra precision mode
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Ben Savage in a high up transition