540s are pretty easy - you just have to have 180s and 360s down good, then go in like you are gona do a 3, but toss it a bit harder with your shoulders.  when you come around to 3, spot your landing, and look at it for a second, but keep rotateeing the shoulders and skis, then at the last second, look up the hill with your head.  they are just like 360s with a little twister type 180 on the end... once you get them like that, you can float them out and make them smoother.