How do I tell a guy I like him?

If you want to or even considering doing it, go ahead and do it! I'd just take whatever comes afterwards, whether that be reciprocation, embarrassment, drama, as an interesting new part of your social life. Other people will soon forget about it, but it doesn't hurt you to try and it's a story under your belt. You'll have no regrets if he likes you back.

just jump in front of him and start singing :

"I REALLY REALLY REALLY REALLY REALLY REALLY  LIKE YOU, I WANT YOU DO YOU WANT ME , DO YOU WANT ME TOO?

OH DID I SAY TOO MUCH?

IM SO IN MY HEAD

WHEN WE'RE OUTTA TOUCH (OUTTA TOUCH) ,

I REALLY REALLY REALLY REALLY REALLY REALLY LIKE YOU , I WANT YOU, DO YOU WANT ME , DO YOU WANT ME TOO?

You can wait for that awkward pause in a conversation, then say "Hey . . . I really like you. I Like that you are kind, and that you seem to actually care about the same things I do. Can we maybe go out, and just see if perhaps we have some chemistry? No Pressure, just some time with just us doing whatever . . . . Dinner, movie, concert . . . Heck even a coffee to start."

You don't have to. Your body language will show that you do.