....practice, stop relying on words and just go out and force yourself to do them.
Just focus, thats all it is.
Focus on the 360 rotation.
Focus on the whip.
Focus on the landing.
Im sorry but i have to say, stop asking people how to do them because it isnt like an answer will make you land a trick, just go out to your skate park or flat or whatever and try them, doesn't matter if you fail at first, think about it, everyone sucks at tailwhips first try, its exactly the same.