Whether he's into sports, video games, movies, or books, talk about these subjects with him. Show him you have an interest in the things that make him who he is. If you don't know anything about these subjects, do a little research. You don't have to be an expert, just learn enough to start a conversation.  Read the highlights from his favorite team's most recent game, then ask him if he caught any of it. Research upcoming video games that will be released soon and ask him if he plans to buy one of them. Don't lie and pretend you know more than you do about these things. Be honest and say something like, “I don't know much about it, but it looks cool.” Show him you pay attention to what he says. Whenever you see him, ask him about something you discussed the last time you were together. If he said he had a big math test coming up, ask him how he did on it. If he mentioned his dog was sick, ask something like, "Hey, is Bella feeling any better today?" Don't pepper him with compliments every time you see him, but find small ways to fit them in. If he shows up wearing a shirt that looks new, or he seems more dressed up than usual, tell him he looks nice. Or, if he has a favorite t-shirt he wears a lot, tell him you like it with a simple "That's such a great shirt." Compliments don't always have to be about appearances. Tell him he has great taste in music or that he's a good artist. Showing him you trust and respect his opinion is a good way to hint that you like him. Ask him something trivial, like, “What movie should I watch this weekend?” or ask something more serious, like, “How should I deal with this fight with my friend?” Be sure to follow up with him the next time you see him and tell him how it went. Find a funny photo or gif and text it to him, saying “This made me think of you.” You'll show him not only that you think of him while you're apart, but also that you associate humor with him. It doesn't have to be funny. Pick an interesting article online and send him the link, saying something like, “This reminded me of our conversation yesterday.” If all else fails, don't be afraid to just be honest. Maybe he has trouble picking up on hints, or maybe he's too shy to make the first move. Try simply saying, “Hey, I really like you, do you want to go out sometime?” If he says no, tell him that's ok. Say something like, “Never hurts to ask,” then smile and start talking about something else.

Summary:
Talk to him about his interests. Follow up on things you've talked about before. Compliment him. Ask for his advice. Text or email him about something that reminded you of him. Come out and say you like him.