95% of the times the problem is in the jump.
Aerial is the the entry level "swing up" move (like the jstep moonkick, gainer flash, webster) where you need to learn to get height from the swing. The other thing with the aerial is the fact that you actually have to jump off of the other leg, and hard. A lot of people can jump really high with both legs, but only 1 inch or so off of one leg. So, couple of tips for training:
Start doing swing-back cartwheels. Basically stand on your jumping leg for the aerial, and put the other foot infront of you, and swing back as hard as you can and follow through with the cartwheel. Do this until you can do it fast.
Learn how to run and block off of one foot. Plenty of tutorials on blocking on the interwebz.
Do one handed cartwheels, either arm, and make sure they are fast.
For the aerial, you are actually jumping off both feet, but only the trailing foot is the one giving you height. The jump with the other foot adds to the swing power. Imagine taking the spring out of your clicky pen, and putting one end on the table, and pushing the other end down with your finger. When you push at an angle, the spring is going to bend and snap out and fly sideways. Same idea for the swinging leg, you wanna jump with it, but translate that jump into the swing.
Finally, USE YOUR ARMS. You want to get your torso around and facing the opposite way, not just upside down. Swing your arms to help you with that rotation, but remember not to throw your torso/arms down, throw them AROUND.
So the dynamic swing stretches with your legs when you watch TV or something, helps you get more power.
Finally practice enough times, and you will finally get it. Everyone does.
