Check out this youtube video with Peter Hayes for help casting.
https://www.youtube.com/watch?v=37ra2wNuzfQ&ebc=ANyPxKrc4CyNxOH_rcLLyzbOSeHWpx3B__6t4X35fiZDaGQv9M_kc-cI3scfnirnVAb0Z4r_5yt72SwWNo4YCfd4rF8cowwOvA
He is informative and entertaining which are great attributes for an instructor. I've watch a couple of his videos and I think he explains things well. Also, he recommends several things you can do to practice and improve your casting.