How do you break up with someone really nicely?

I really need to break up with someone because I honestly could only ever think of him as a friend, and I like someone else, and I feel really guilty staying with him, and think he deserves someone that likes him back. What should I say?How do you break up with someone really nicely?
Tell him the truth. He will be hurt, but the sooner you do it the better it will be for him. It's very important that you do it in person if at all possible. That way you can give him a hug and tell him that you still care about him as a friend. After that, give him some space. He will come to you when he can handle being your friend again.