The follow through (or lack of) may be one of the worst problems I see at Newville Little League other than kids throwing from their ear instead of using the BIG "C".  Kids either don't follow through, or they follow through incorrectly.  The worst thing you can do is stop an object quickly, especially your arm.  What's that one law of physics say... an object in motion tends to stay in motion.  So, slow your arm down slowly, and it will last a lot longer.  Here is something I tell the younger players.  Tell them to tickle the grass with thier finger tips.  During the follow through, the arm should finish (for a right hander) on the left side of the left leg down near the grass.  Thus tickle the grass.  It helps to remind them that their hand should end up near the grass after the throw.  I have seen a lot of kids throw across their body and finish with their right arm near their left elbow.  This is BAD, if you see this, it should be corrected ASAP!!  Oh, by the way, just make sure that they continue to look at their target during the follow through, or they may begin to throw the ball in the dirt.  Keeping their eyes on the target will help them release the ball at the proper time.  If they are a pitcher, their back leg should then come around so that they are in a good fielding position after the throw.  This way they will be ready for a possible line drive back up the middle.