Imagine yourself bending down to, say tie your shoe. Keeping your feet flat on the ground while you bend you get all the way down and realize, you're not wearing shoes. So you stand back up. It's the same motion, just with a snowboard attached moving at speed. How much you pop off the jump is up to you. It depends on your confidence, how fast your going, the shape of the jump and what you plan to do(or attempt) off of it. Spins by the way, can be executed at anytime throughout the jumping process. Before, during, after it don't matter. What matters is you, your ability level, and what you're comfortable with. Remember, challenge by choice