How do you get close to someone ?

So the thing is, for a while now I have this huuuuge crush on this guy, but he's cute and I'm shy and I have no connexion whatsoever to him. But he's the kind of really sweet and cute and kind person, you know ? like somehow if you go talk to him he won't be rude and will keep talking with you somehow. But even so.... It's been a while since I'm in love with him (I got it rlyyyyy bad) and there's only a few month until we'll quit high school but I rly want to be in touch with him bc I rly don't want to give up on him. The few times we talked were nice and I know we would at least be friend bc we're not rly different you see ? we just need to talk a bit.... But it's rly hard for me to go talk to him, we don't rly hang out with the same people and he's rarely alone on his own. I thought about talking to him on facebook but like what do I say ???
I mean, my problem is, how do you go and talk to people that aren't your friend ? How do you make friend with people ? What should I say to start a conversation with him ? Or maybe, should I directly go to him and tell him I like him ? Wouldn't it be weird ??