Launching obstacles rather than rolling off them lets you maintain momentum and flow on a sweet trail, helps avoid gnashing your big ring and makes you feel like a demi-god. When executed well, there's less to go wrong as you fly clear of any nasty roots and evil rocks.
Landing on both wheels is standard on the small stuff, but touching down the front wheel first is smoother - mandatory when the landing is steeper, to avoid whip lashing your body forward. When you've got it right, the rear wheel contacts terra firma at about the same spot as the front wheel. As the front end drops and you bend your legs, your seat is inclined to shunt your butt - upsetting both your technique and dignity. A tab of Voltaren and lowering your seat post 5-8 cm should sort that. The technique is a tad trickier on larger drop-offs with either a flat landing or not enough run-out to hit at speed. It usually involves a slow wheelie, pedalling as you roll off to keep the front wheel from dropping. Land back wheel first, compressing legs then arms to eat up momentum.
The other angle on airtime is jumping, that is deliberately gaining altitude. As you'd expect, once you're in the air the technique for landing is essentially the same as drop-offs. Typically you're flying over a roll-over or popping off a rock, root or stump and landing lower down the track. The technique is quite intuitive. You can either un-weight your bike at the top and execute a delicate bunny-hop to follow a natural arc, or work the jump... crouching down on approach, uncoiling your body up at the foot of the jump and extending your arms and legs into the face. How hard you push determines the extra lift at the top. Remember once airborne to draw the bike towards you by bending your arms and legs. Stay relaxed and enjoy the view. Bon Voyage.
To jump, or not to jump: that is the mountain biker's question:
Whether 'tis nobler in the mind to suffer
The rags and chortles of outrageous riding mates,
Or to launch your bike off a ledge of troubles,
And by a clinched sphincter, survive?
To jump: to land;
Once more; and by a landing to say we end
The knocks and grazes
That lycra'd flesh is heir to, 'tis a consummation
Devoutly to be wish'd.
To jump, to land;
To land: perchance to live: ay, there's the rub;
For in that leap of faith what second-thoughts may come
Of clipping free and bailing for the trees
Must give us pause: there's the respect
That makes calamity of such big drop-offs;
For who would bear the whips and thorns of the blackberry patch,
The giant gum's unbending armour, the proud man's shattered GPS, The pangs of dislocated joints, the pretzel'd wheel's delay,
The insolence of others and the 'bagger' spurns
That patient merit of the unworthy sixteen-year-old-with-8-inch-front-'n-rear-and-no-mortgage takes,
When he himself might his timely demise make
With a soil-sampling endo?
Who would take the pain,
To grunt and sweat under a weary granny-gear climb,
But that the hope of nailing that gnarly drop-off,
The undiscover'd nirvana that once found
No mountain biker ever returns, puzzles the will
And makes us rather bear the opt-outs we know
Than crank hard at those ledges that we know not of?
Thus Wang Chung does make cowards of us all;
And thus the native hue of car-park bravado
Is sicklied o'er with the pale thought of a yard sale,
And yumps of great hang-time and distance
With this regard our wheels hug the dirt,
And lose the catch of air.
Danny Trudget (with apologies to The Bard)