Originally Posted by DobeSpell

I'm not a professional trainer but this worked for me. I throw him a ball, say Stop! and hold him. Then let him go.
After we practice it, I'd let him start chasing the ball and then say stop!.

He learned pretty fast.
Now I repeat the command whenever we play. I throw the ball, he starts running, I say Stop! Come!, he stops, come to me and then I let him go again.
This works when he chases cats too, and he has pretty strong prey drive.