How do u teach a gsd to retrieve?any good references or ideas?

I have a german shepherd. I showed him how to fetch by kicking a soccer ball and he would go and chase it and eventually bring it back. Then i showed him that i only kick the ball if he brings it back near me. Then he caught on and understood. Then i later started throwing the soccer ball. And later replaced it with a stick. Now he plays perfectly. Remember no playing or petting until he brings the ball back to you . Just stand still do nothing and show him you can only kick the ball if he brings it back.