I've always found it hard to explain the different rail tricks. I think the best way to learn them is through video games. Video Games? I know right. It sounds stupid but it works. I learned most of my skateboard knowledge from playing skate. I feel the same thing can help with skiing.
Go to gamestop and buy a copy of EA SKI. It should be less than $20 if they have it. I saw it used for $13.99 a couple months ago.
Buy that game, just be sure you don't have anything you have to get done for the next 2 weeks or so. It's addictive.