[TheAlchemist]

You're asking the right question, but I suppose not in a right way. From my experience you need to show them that it's the company culture to challenge things in a smart and constructive way. To do that, you do nothing very formal, just sit your best guys with the newcomer, explaining how things works and why. And sometimes, criticizing the current stuff, but not in a authoritarian way - something like we know we can do better, just nothing really worked well or we didn't have time but now we do.

That way it feels much more like -> we have something we could do better, and the guys are trying to improve that, let's do that with them. While 'critique' immediately feels negative and kind of creates a barrier.