Keep that elbow nice and tight to your body. Concentrate on keeping it behind the ball as long as possible. Focus also on staying nice and upright at the foul line with your body (bend with your knee, not your waist, since the waist can bend you forward OR sideways) -- improving your balance and posture can help bring your arm back closer to your body.
If you have a video camera, or a digital camera that does video at least, take it with you to practice sometime when you're working on your armswing. Immediate feedback from seeing yourself throw the ball, instead of just feeling it, will tell you a lot.