Like the smart guy above commented, join the trick tip cult, heres a link:http://www.newschoolers.com/ns/cult/home/id/1690/t/Trick+Tip+Forum/
My only advice, being a fellow amateur would be, practise getting comfertable in the air by doing simple grabs, then practise 180's popping off/onto the piste or off little bumps then when you feal you're ready, try an throw a 3.
When it comes to boxes/rails, DONT LEAN BACK this is almost a reflex for most people (including me) and it throws you back and gives you some nice hip bruises. Consider getting padded shorts if your gonna have a box/rail jam.
Another thing is, you can't go half-hearted. GO BIG OR GO HOME!
Good luck man!