I would rock it indirectly.
"Hey, friend, I just saw this article on common interview trip ups; not sure if any of these apply to you, but maybe worth a read so you can knock the next one out of the park!"
Then, if he doesn't pick up on it, I would engage him in a conversation in which I steer him into realizing it for himself.
"My friend so-and-so is a recruiter, and you would not believe what she told me about last week! This guy came into an interview and had a bolo tie and a booger in his nose. I know, right? She said she gets these people all time. People with dirty nails, nasty coffee breath, uncombed hair, missing teeth... she went on and on and said there's no way in hell she'd ever hire any of these people. Sounds like a crazy job, Makes me think about the interview scenes in step-brothers! "Pand? There's a 'd' in it?""
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