Imagine that you are trying to get on a bike. This is one method of getting comfortable with the feeling of a waltz jump).
As you start the take-off, you should be leaving the ice on your left toe-pick so it is the last part of your boot that leaves the ice. Never rise off the ground on a flat blade. Never think of rotation; if you are in the right starting position you will automatically make the half rotation necessary.
You may not feel comfortable doing the jump starting on your left foot and landing on your right. This turns you in an anti-clockwise direction. If you generally turn in a clockwise direction try reversing these instructions and starting on your right foot and then landing on your left. Which ever you choose stick with it and if you try spinning on the ice make sure you’re turning in the same direction. It doesn’t matter which way you turn but you need to jump and spin the in the same direction.