How to 360
As you go off of the jump, have your arms out in front of you and look at your left arm, flex your stomach, and when you have done a 180 be looking at the takeoff, this will get you spinning a little forward so that you will land flat on the landing, look back behind you and pull your knees in a little. The rest will come naturally if you have done this.
How to 720
Well first, you need to be brave. Next, as you are going off of the jump, start spinning as if you were to do a 360 and when you hit the 180, and not a second before, tuck your arms in as hard as you can for a full 360 so you will be at a 540. Then just go one more 180 as you spot your landing. GREAT. Thanks for reading.