I have no idea how to tell apart gays from straight guys except by outwardly behavior. I never socialized much with them because my interests are so far apart from theirs. However, I gained some as family (in-laws) through the wife. I treat them as family. When they visit, they greet me Pinay style. I sometimes wince when they hug me.

But, they're family and they're welcome to stay over as long as they want.
My limited experience being around gays so far has indicated they're not attracted to straight guys. Rather, they're attracted to their own kind. I'm not too worried about a gay guy making a move on me.