How do you get someone to tell you some thing that is wrong? :-}
also its a guy
Don't ask "What's wrong? I know something is wrong, why won't you tell me?" Instead, say "I get the feeling something is bothering you. We can grab a beer/Coke/coffee if you ever want to hang and talk."
go up to him and say: "You did it wrong!", that's what i would i do
You can't make someone open up to you...just be his friend, show him you have his back.If he feels safe with you he may then tell you.
let them know that whatever it is..you want to help..and that you are on their side..