sit down on the ground. tuck your knees to the chest. then rotate your legs side to side, 10 times to each side, without moving your upper body
then do the same thing, this time your knees not tucked as close
then again, except this time you lay down, and unbend your knees completely
then stay laying down, and open (as far as possible) and close your l-3-g-$ as many times as possible
then do bicycle kicks laying down, focusing on tucking your knees when you come in. as many times as possible.
do 2-3 sets