With most dogs, this means entering a battle of strength, where the owner tries to prise the dog's trophy from his clenched jaws. This is going to end badly, most likely with the dog eating a toxic amount of chocolate, a trip to doggie ER, and the owner getting bitten into the bargain.
How much better would it be if the dog knew and obeyed a command to let go of the ill-gotten-gains? But the advantages don't end there, because you can use similar methods to teach a dog to let go while playing tug. This is an important way of allowing him the thrill of tug, but in a way that has him yield to you without argument.
A dog is never too young to start learning "Leave" and done correctly, it makes a fun game for even a puppy to learn. Of course, always work to the principle of making training fun and rewarding the dog when he performs the desired action. Aim for short training sessions, of say 10 minutes each, several times a day. If the dog gets confused then draw the session to an end and start again later. But make sure to end on a positive note with a command the dog knows and gives you an opportunity to praise him.
During your practice sessions, never be tempted to use force to retrieve an object from the dog's mouth. This is counterproductive, as it stimulates possessiveness, which is the exact opposite of teaching the dog to give objects up willingly.
To get started you'll need: