Know that he likes you. If you don't absolutely know that he likes you, don't act upon it. You may ruin a friendship based on rumors that other people have told you or an assumption that you've made because you think he likes you. There are some tell-tale signs that he is truly into you.
He consistently asks you out.He persistently tries for body contact.He persists on hanging one-on-one.
Don't procrastinate. The longer you wait, the worse it'll be. His feelings will grow and it will be impossible to maintain any kind of friendship after you tell him the truth.
Don't avoid him forever. You can pretend all you want that he'll "get the hint" if you simply avoid him. Well, he won't. You need to find a time to talk to him. Make it a time when it's only the two of you, so that he doesn't get embarrassed in front of a group of people.
Make a plan. Write down what you're going to say before you say it. If you fumble over your words, you'll make the conversation longer, more awkward, and a worse time than it needs to be. In your plan, you should have some points about why you aren't interested in him. Don't attack him with reasons he's gross—just be honest about why you're not into him.
You can't seem to move on from your ex-boyfriend.You just aren't physically attracted to him.You like someone else.
Talk over the phone. If you have a conversation on the phone or over text, you can still implement all of these into your conversation. The most important part when doing that is being ultimate. Make sure he knows that there is no future chance for the relationship.
Acknowledge the seriousness. You need to let him know that you want to have a serious conversation. This way, he takes what you're saying to heart. If you don't take the time to do this, he may not understand the level of importance of the talk.
Be nice. Let him down easy. Add a compliment or two into your talk but convey to him that it's not enough.
"You're a great friend, but we can't be together.""You'll make someone very happy, but it's not going to be me."
Give him your "back-off" message. Even after giving him the reasons you're not into him, he may not fully understand. Deliver your official "back-off" message after you've told him your reasons.
"We won't have a romantic relationship.""We can stay friends if you're going to keep it at friendship.""There isn't the right chemistry between us."
Ensure him that your feelings aren't going to change. If you don't tell him flat out that you're feelings aren't going to change—he might hope for it. Don't let him leave with any questions of you having romantic feelings for him in the future. Set some ground rules for your friendship (if there is still going to be one).
Be honest. Let him ask some questions if he wants to and answer the honestly. There's no sense in protecting his feelings with lies: tell him the truth. This will help him move on more quickly.
Be willing to listen. Rehearsing the conversation in your head helps, but can also hurt you by creating preconceptions in your head about how it will go. Rather than attacking him with your thoughts, sit across from him and hear what he has to say so that he will listen to what you have to say.
Agree to end the conversation. To ensure that he's gotten your point fully, ask him what he thinks about it all. Stand your ground and don't leave the conversation without him understanding that you don't like him. Don't leave without clarity.
Be polite. Just because you told him that you don't like him doesn't mean you have to ignore him or be rude. Don't think of him as weak or broken because of your choice. He'll move past it, so treat him like a human being. Don't just ignore him forever.
Give him space. Don't go out of your way to see if he's doing alright. If you run into him, be cordial, but don't reach out to him outside of that. Rejection hurts, and if you're constantly reminding him about it, he'll constantly be hurting. This could eventually lead to self-esteem issues, anger, or even aggression—you don't want to be at fault for that.
Don't lead him on. If he decides that he can stay friends with you after having the conversation, make sure to set a clear line of appropriateness. This can be in a separate discussion if either of you need time to think about it. Having this discussion will help both of you put some closure on the previous one.
Discuss if it's ok to comment on how one another looks.Talk about if physical contact (hugs, holding hands, etc.) is still appropriate.Throw a few compliments into the conversation so that he doesn't get down on himself.Don't be surprised if he gets angry or defensive. It's not easy to take rejection.Before you have officially decided to tell this person you don't feel the same way, make sure you to don't really like him or her in any romantic way, only as friends.