In the clip below Carrie Lane, University of Nebraska Throws Coach; assistant coach in 2009 and 2011 World Track and Field Championships, demonstrates a method to teach your discus throwers how to main posture, balance and alignment, while allowing them to improve their kinetic linkage and ability to maintain separation. Coach Lane also does a great job of taking you through some of the common mistakes that throwers make.
The drill is from a complete DVD on throwing the discus. For more information click the link Becoming a Champion: Discus for Girls’ Track & Field
The YouTube video has sound so, please make sure that your sound is on and that you have access to the site (some schools block access to YouTube)