The key is to hold jump key from a distance, and release jump key slightly behind the edge (for knees to expand) in speed for maximum heights, meanwhile make sure every button is released, including left stick, then you can quicky go back and do tricks with left, right sticks or triggers in air. You can also turn off 'safe tricks' in options which allows you to have better chances to perform tricks.

If you're going too high, optionally you can grab the board in mid air, let go few seconds before to secure landing, give it some time to straighten position, and prepare to slow down to reduce g-force right after landing.

Have you ever seen a giraffe snowboard before?
Notice the giraffe landed first at the direction he wants, then slow down or make s turn to regain g-force. If a giraffe can do it, so can you! :)