If you have issue triggering those basic tricks, make sure your timings are correct (for jumping and rotating with the left stick). You should also avoid pushing the left stick in a direction before jumping. Secure your trajectory to the jump opportunity, release the left stick and then prepare your jump. Train and repeat to get the feeling!
For the most advanced moves, use the right stick up or down as soon as you jump for flip moves. In the air, press and hold triggers for grabs with the left, right or both hands. You can tweak your grabs once set using the right stick.
If you want to know more, we recommend watching this video:
The video will explain the system in more detail and should give you a very smooth start to the game.
See you on the mountain!