Tennis ball (easier for puppies) OR other favorite toy
STEP 1: Have your puppy near you on the long line. You can have the line short at this point to keep them near you.
STEP 2: Throw the ball as you say "get it".
STEP 3: (Super important for the bringing back) Wait until your puppy latches onto the ball before saying "let's go". DO NOT say "good boy" or "let's go" until they have a grip on the ball.
NOTE: If they don't go after the ball, first make sure you have not picked out a time the puppy is tired or has already trained enough. Remember you want to do this when the puppy is fresh and ready to go. If they are, but something has just distracted them or inhibited them, go towards the ball yourself with the puppy. They will normally go and grip it after this.