How do I tell I'm no with out hurting his feelings?

As a guy, I have had tons of girls friends tell me that their friend doesn't like me, well I've had many girls lie to me on that point. So generally I only believe what comes from her mouth, meaning, if you want to tell this guy that you only like him as a friend, you had better tell him yourself, face to face, nicely but firmly, and alone; and be ready to defend why you only want him as a friend. Stop having your friends do the dirty work for you, generally if he's a decent guy after you tell him he will get the hint and move on.

I think there's a couple of things you could do. Obviously, the best would be to say, "Look, you're a really nice guy, but I'm not into you like that. " or something to that extent. If you want to go a little more indirectly, if you like another guy you could casually mention something about him and usually the guy will get the point.