How do I tell him about it? Is this the right thing to do?

I think number three would be to make subtle moves like occasionally brushing up against him and such and see how he reacts. if he shows no interest then he's probably not gay. If he does react (more than once) than you just might have a chance. get him to be one of your closest friends and then you get to be with him a lot. at some point he might show interest in you so should take advantage of that. You should have a good instinct once you reach that point so you wont need advice. Hope all works out!!! :)