How to tell if your friend is gay is something that you might want to think about. In this day and age, gay men are coming out of the closet much sooner than before and that is if they were ever in the closet at all. Some men might hide their homosexuality from their closest friends if they are afraid it will hurt their friendship. Many straight men can carry on best friendships with homosexual men without sexual orientation ever becoming an issue.
Watch for the clues. Although you may or may not be the source of his affection, you may notice little clues as to how he interacts with other men and women. Most heterosexual men will flirt at a certain level with any and all females. It could be a friendly smile or even being a bit rude. A gay friend will be more on the same level as the female talking about shoes and clothes but not in a flirtatious way. When they talk to men, they are interested in that you may catch actions that would be associated with flirting: hanging on their every word, eye contact that lasts a little too long, and maybe touching another man when they are talking.
Listen to them. When a gay friend is talking to you they may be trying to tell you that they are gay. When you are talking about your most recent conquest, they may not pay attention or even tell you they don't want to hear about it. A gay friend will most likely not talk about a woman they find sexy, but they may talk about a man they admire. They might mention a man's rock hard abs or muscles or other things that a man would normally find attractive in a woman.
Don't judge. When you are with your friend that you think may be gay don't be quick to judge. Be careful of the things you say about gay men. If you truly care about your friendship, you will try to understand how he feels and not judge him.