You will actually be training your puppy every single time you interact with them!  Your dog watches everything you do all they time.  They actually learn to predict you actions before you even do them.  It is really kind of scary that they are that observant.  When you are working with them on a specific item, all lessons should be on 1-3 minutes long.  Retention is much better if you even play prior and after working on a behavior.  This sets your puppy up for success each and every time.