What do I do if a guy likes me and I'm not gay and I'm a guy?
Just say plainly that you are not gay. In a way, it COULD be a good sign for you that a gay guy likes you because if he is one of those with impeccable tastes that means you probably have a lot of female admirers as well.
Then tell him you don't feel that way. It's the same thing you do with girls you're not into.
Nothing unless you want to, it sounds like you're not to sure. It's simple enough to say thanks but no thanks, or back the **** up, depending on your style
Just say no thanks the same way you would to a girl...