How to find out if someone is gay?

There really isn't a way to determine whether someone is Gay or not unless they tell you. I mean you could stumble upon them making out with someone of the same-sex, however the chance of that occurring is probably lower then a repeating 1 in 4,096 chance or even 1 in 8,192 chance.

The best thing you can do is attempt to become friends with them first.

You can start by asking him if he likes Broadway Show tunes.

Then ask him what he thinks about Shawn Mendes.

Ask him.

You ask, or they tell you.

So ask him out. If he's gay or bi he just might take you up on the offer. If he's straight he will let you know he's not interested.

Out your self to him. Don’t say you like him though. If he maintains he is straight - just move on - you can still be friends. But if he outs himself back, then you can find out out if the feeling iS mutual.

Try asking him first before assuming that.

Ask him. Even if he is, he may not be into him. Life can be cruel that way.

If he gets an erection from the scent of your diarrhea, he's your man.