When he drops it, that is your signal for the game to resume. I have used retieval as an example. These same priciples can be extended to other constructive behavior, also. It all depends on each puppy's aptitude for that skill. Tracking is another aspect that the ATS can exel at.
Obedience is another.
All training is really just an extension of obedience. This method entails teaching the puppy that a food reward comes from the mouth, or appear to. For those that have a problem rewarding food from the mouth, you will have to hold the food beside your mouth with your hand. I just find it more efficient to reward directly from the mouth. This is the best was to establish steady eye contact.