The frindzone

I've been in your exact situation before. If it's one of your good friends be gentle about it, he should respect your decision. Talk to him about it, if might be too hard for him to "just be friends with you" and maybe you guys could go your separate ways. or maybe he can accept that you don't feel the same way and you can continue to be friends. If you do stay friends though, be considerate to his feelings. try to avoid things like talking about your crushes with him, etc. my inbox is always open if you want to talk about it :)

Something along these lines should cover everything and give him the best thing you can give him: what he needs to move on.
"No matter what you may have assumed till now, and no matter for what reason you assumed it, I have no romantic interest in you whatsoever. I am certain I never will. I expect that knowing this, you’ll put your attention elsewhere, which I understand, because that’s what I intend to do." From 'The gift of fear'.

The simple truth is always the best in these situations. Tell him you value his friendship and that you hate the thought of hurting him, but you just don't feel the same way.

oh my god. i exactly know what you are feeling at the moment. Ive been through this situation three times. all i can suggest is you should tell him what friend zone is. tell him its better to be friends forever rather than being each others ex. because breakup is what happens as a result of relationship. or maybe stop talking to him.

For Start You Can go out with him, try to be with him, maybe you will like it. And if not, you can just say, that your sorry and he knows you pretty well, so he may know that hes not in your style, that will help. I hope i helped you.