When you do your critique, always start with something positive. Even if it has to be "It sure was a pretty plane before ......... and the engine ran good until impact". OK, a little levity there but get on a positive note before you start to gently point out faults. Always present a method to correct the faults also, don't leave them hanging. Don't say "Boy, you sure blew that landing" and just walk away. Tell him what he did wrong and how to improve it the next time.