My puppy barks at me when I tell him off – what should I do?

Your vet has given you some poor advice and really needs to brush up on their animal behaviour studies. A mother dog only picks up her pups by the scruff during the first few days of their lives, and purely to move them around—never to discipline them. So, picking a puppy up by the neck and shaking it "just like its mother would" is a total myth, yet it’s still a very common misconception. Maternal correction happens later once the puppies' motor skills have developed, and this is done through growling or a gentle nip. The forced submission technique you’ve been told to use is also terrible advice and is being used completely out of context. Doing it this way is an act of aggression towards your puppy. This posture is something a dog chooses to do of its own accord when it decides to show appeasement. If you force them into it, the message loses all meaning. Imagine this scenario: a stranger grabs your hands without warning and forces you to put them in the air. You’d be thinking, "Who is this nutter? What do they want?" and you’d be perfectly justified in feeling confused and annoyed. Now, imagine you’re in a bank during a robbery. You choose to put your hands up yourself to show the attacker you aren’t a threat. In that situation, you are submitting to the attacker by choice. In your case, your dog only feels like they're in that first situation with the stranger. You need to rethink how you discipline your puppy and, above all, look at when and why you are punishing them. Are you interpreting "naughty" behaviour from a human perspective? Is it because you haven't anticipated a situation properly or haven't explained what behaviour you expect? Is it fair and appropriate?