For the record: there is no foolproof way to know if someone is gay.
Sure, there may be hints, but there are no universal signs that apply to everyone all the time. Really.
Back in the day, there were a lot more myths and stereotypes about what it meant to be gay and people believed a lot of misinformation about sexual orientation.
According to the Guide to Gay Life:
"Many decades ago, some gay men would use left and right side signals to indicate their sexuality or preferences in bed. This was back in the days surrounding Stonewall when being gay meant an instant beat down or arrest. We had few choices but to use Bat Signals to find each other. These indicators, though no longer used today, lived on and spread outside of the gay community. They eventually developed into perhaps one of the silliest stereotypes about gay men. Every man was terrified that if they got their ear pierced on the wrong side they would be tagged a homo."
Yet a lot of people of all sexual orientations still look for signs. Sometimes there are clues can mean that someone is gay. Other times, something that seems like a real indication is just a product of stereotypical beliefs, or the hopes and fantasies created by someone with a crush.
As one teen says,
"So there's this guy from my school who I'm starting to fall for. He was in my health / PE class last year and that was when I really started noticing that I like him. One day he smiled at me really big at the grocery store which really caught my attention and started to make me wonder if he's gay too.
Throughout the semester I noticed that he would lift weights next to me but I don't know if it's just coincidence. One time, he even asked to be my partner for this exercise, but I was stupid and chickened out when he asked if I wanted him to hold my legs down. I know that was a big mistake and I'm kicking myself for it. Now this year, I have no classes with him which sucks. But every time I see him in the halls my heart beats really fast.
What makes this even more complicated is that he doesn't know that I'm gay because I haven't exactly come out to everybody yet. Any advice would be great."
There is no way for me to know if any of these anecdotes mean that this guy is gay. One idea would be for this teen to come out to the person because that might prompt the guy to do the same. But this tactic can be hit or miss since the guy a) might be gay and still not come out, or b) not be gay in the first place.
Another idea is to ask some questions, like "So, what do you think of gay marriage?" Or, "Think you might join the GSA?" Keep in mind, the answers might not prove anything conclusive, but they might be a good way to start a conversation about being gay.
Finally, there is always the direct approach, which basically just means asking a guy if you think he is gay. This is really, the only way to know someone sexual orientation. While a lot of the signs you might be looking for (an interest in certain music, fashion, or design, for example) may be stereotypically associated with being gay, gay men, like straight, have a wide array of interests and mannerisms which often have nothing to do with a person's sexual orientation.