Generating speed is by pumping... either short, rapid pumps driving off the fins and flex of the board, or big climb-and-drop pumps using gravity and down-the-line wave energy. The faster you go, the higher/further you'll go in the air, but you can still pop off the lip without going that fast, which is how you can start to learn. Start your turn no further down that at the bottom of the wave... not out on the flats. If you're not going that fast, you can take a more vertical line up into the lip... the faster you're going, the more horizontal your line to the top of the wave can be. Aim for a section of vertical lip and time it just right. Like any good turn, start with your shoulders and let your hips follow, then feet. Develop a sense of where the board is under your feet, because you'll loose contact more often than not. Wind direction and strength are key... as said above. Good luck.
I agree, I see a wider stance change during the air process at times. AKA currently in the quik pro right now.
now... I have never done an air on a surboard but I do believe that the mechanics are very similar to doing an olly on a skateboard. on a skateboard, your stance is closer, meaning your feet are closer together then normally would be. then after you slam the tail on the ground, your front foot is dragging the skateboard upwards. resulting in a wider stance while in the air and landing.
Im guessing that these surfers are dragging thier front foot upward along the surfboard to help raise it higher.
But like I said I have never even tried getting an air on a surboard, but I might now. lol.
I think of it as... there's an ollie type air and a ramp type air. If you're looking to use your speed and really boost one, you're not so much jumping from the lip (ollie) as you are launching/rotating, unweighting/compressing, then extending for the landing. I never really got good at it, but when I've done it, that's how it feels.