No Talent in Consoling

Agreed with Kat: listening is the best you can do. Appear interested if it's not coming naturally to you. For instance, asking questions that show you're listening and thinking about what's being said, bringing up similar experiences that you've gone through, and even sometimes distracting them by going out and doing something fun with them if they're game enough. Ultimately, he's going to have to figure stuff out by himself, and the best you can do is give him support until he does. But if he ever mentions feeling suicidal, that's when you should get professional assistance, and immediately. Well, not mid-conversation, but you know. Soonish. That's a costly lesson that I'd rather have learnt otherwise, so don't make the same mistake I did...

Jam it back in, in the dark.