Not a perfect throw, but video yourself and compare stills with:
http://commons.wikimedia.org/wiki/File: ... tt7435.jpg Most likely you'll find improvements. Important things, stay closed as long as possible and let your arm come as late as possible, picture 1 and 2. In fact you throw with your body, not with your arm, the arm movement is on top of many other movements. With a runup, even a slow one, try to land with both feet at the same time. This is not really possible but when the left foot lands shortly after the right you get a better block. Do not bend much in the elbow, both for throwing far and for preventing injuries. And when you reach that 30 meter mark, ask for further advice on
http://disc.yourwebapps.com/Indices/109718.html