i found that, at first, if i thought too much about it right before i attempted to hit the rail i wouldnt be able to do it... practice, my friend. tahts basically it. i mean, you can try to think about all of these things (which really do help in the long run..its just a lot to think about..)
and, i mean, you're gonna fall. its inevitable. but you learn from your falls. so in the end it all works out. my advice: start boxes, if you can do them well move on up to rails.. but start with a straight rail close to, if not on the ground.
hope that helped.. good luck