You can't. The only way you will figure it out is by asking.
Guy: Hi!You: i'm gay.
You can tell that some guy is gay by asking him his best friends, and by observing his behavior about other men.
If a gay guy likes you and you are not gay, then nothing happens. If you are gay and you like him, you may want to tell him how you feel.
Ask him
If you are gay, just be completely honest with him. I am a straight guy, but I have a friend who is gay, so I do know this. Just tell him that you understand that he is straight, but that you have feelings for him and you wanted him to know because you felt that you needed to tell him.
Girls can tell or know if a guy is gay by observing his behavior in a group of men.
Tell him a joke.
It's basically the same process as a boy and a girl,there is no difference
There is no way to tell for sure if a guy is gay. There are stereotypical signs that people consider tell tale signs that a guy is gay, but they're not always true. The only way to know for sure is to ask them. They may or may not be comfortable telling people if they're gay.
because i have a friend and hes gay last time he went to my house and he star to touh my penis and he tell me that he was in love wiht me and i got scared and ran out of my house.....so thats who i can tell a gay guy like's me
Ask him
just write a note