1/4 Pipe Air
Description: 1/4 pipes are fun, and I'm a vert rider, once i learned 1/4 pipe airs I was hooked. But a 1/4 pipe air is when you roll up a 1/4 pipe, out the top (or inside the ramp) and come back down forward. I'll give you guys fakie airs later.
Pre-Requisites: You should know your bike by now and be able to move your bike in the air and do a decent bunnyhop. You also need to know which way you spin. Most of the time it goes like this, anything else is goofy footed:
Left Foot Forward = Spins to the right, clockwise
Right Foot Forward=Spins to the left, counterclockwise
What You Need: A 1/4 pipe of course, a halfpipe may be better because in general 1/2 pipes are wider and easier to ride away safely if you screw up.
How-To: 
1) Approach the ramp at the angle you're going to spin. If you spin clockwise / to the right, you'll come from the left side and down the 1/4 pipes right side.
2) Start out carving the ramp carving at a smaller and sharper angle each progressive time, this will help you get the feel for 180's a bit.
3) When you're done "feeling the ramp" you're gonna bunnyhop off the ramp (when you have reached the peak of your imaginary carve) a little and go into the spin, this is how the spin goes:
    3a) Turn your bars towards the landing pulling with your arms.
    3b) Kick the frame in the spin with your legs. 
    3c) theres a lack of perfect nose-dives in the world, nosedive it too.
4) You should be rolling away if you did it correct, if not, you can fudge it a little by pointing your handlebars towards your landing and it'll help you cheat your spin out of a full 1/2 rotation.
4+) After you get 1/4 pipe airs INSIDE the ramp down, then you go at the ramp faster and faster until you're blasting big ol' airs. But with bigger airs remember to keep your handlebars pointed towards your landing.