I think the most important thing is to make sure that he's gay. Otherwise things might end up as hell for you.
Unless you're a woman of course.
Oh, and single.
But yes, just like the other comments, try to just give the guy you like a smile. If he responds then you can proceed to the 'getting to know' part. If he doesn't, then he's obviously not interested in you, so don't try to pursue that guy anymore.
