Depends on how you are trying to learn it - from a full run which is more common to cheerleaders and street tumblers, a side chasse which is more common to dancers and gymnasts on floor or a step hurdle which is most common to gymnasts for beam. There are many ways taught to to throw your arms (from a cross throw to just pulling them in to your body to keep from touching the floor)but to land an aerial consistently you need a powerful lunge followed by an explosive drive of your back leg up and over your head. (What was called above the set) The chest remains up until the last possible second. Don't drop chest until after the rear leg has been powerfully driven up. The aerial should lift up and over not looking like you are throwing your chest at the ground.
I teach them standing off a fully folded panel mat first, then lower the panel mat. Lots of body position drills to get the athlete to get in the proper lunge and lift position. Usually once the athlete truly understands what their body is supposed to do and what it should look like when performed correctly, it does not take long at all to start landing the skill.