There is no technicality behind the term "Gaydar" as it is supposed to make a person know the possibility of another person's sexual orientation through a few indications which are completely physical, sexual, and emotional. Of course, many dating apps developed a little technical factor added to this term to know whether a person belongs to the queer community or not, only when the other person also uses the same platform to find his/her interests. But what if the person whom you find attractive out of nowhere and randomly, don't use such technical platforms or dating sites? How come you get to know the preferences of that particular person?
It's hard for a person to randomly guess the other person's sexual orientation or preference and it's uncivilized if you guess it wrong and make a big fool out of yourself. This is the time; you must listen to your heart, not your brain. This is the time you must be emotional instead of technical. This is one of the problems in the queer community. Have you ever found a man very attractive and thought many times before approaching him, just because you are not sure whether he is also into men or not? This happens to all of us, especially gays, lesbians, and bisexuals.
If it's a Pride parade or a queer carnival or any event related to the LGBTQIA+ community, you will never hesitate to talk or approach to know about a person because by default you believe that people who participate in such queer events must be from the community or could be allies. There's no much harm in approaching random people in any of the queer events. But, the scenario becomes completely different, if you want to talk to someone other than any queer events. So, before approaching the person, you like, be aware of the situation and the events around you. Who knows you may hit on your third cousin in one of your family get together events without being aware of the relationship between you and the person whom you got attracted to.
Notice the people around you and evaluate whether they are queer-friendly or not. If you find a group of boys joking around some topics such as feminism, homosexuality, or typical masculinity, then do not even think of approaching one of them, because a true queer person can't stand such demeaning people. So, your so-called attractive person could be a typical heterosexual who also could be homophobic.
Some encounters are knowingly repetitive. Be smart enough to enlighten them. You may like a guy from a house party your straight friend is hosting. But you can't just approach him and ask him to tell about his sexual preferences because that may make you end up in unpredictable situations. If you bump into him accidentally and if you feel the positive vibes from him, just hold on your horses. If he manages to come across your paths, several times with a smirk on his face or if he tries to make a conversation with you, then yes, you need to highlight it and talk to him to know his intentions.
Don't misjudge anyone with their fashion choices because nowadays, many heterosexual men and women are following the metrosexual trend by choosing the style statements and giving tough competition to gays. But if you want to try, you can clearly sense the mood of detailing in a person's style statement to guess whether he is homosexual or whether she is into women or not. If you like a guy and if he dresses up well, doesn't mean he is gay too. But there's a slight chance if he focuses more on his detailing and knows how to pronounce the brands he carries. Hence, try praising his fashion choices and talk more about your interest in noticing the details.
Gone are the days where you judge a person's orientation through his occupation. Don't be stereotypical. But you can give a guess how one is carrying himself/herself with others during his/her work times in his/her workplace. Focus on the hints. You may like a male nurse, who is good with you during your doctor visits and you may feel him as attractive too. But try to analyze whether he is the same with everyone or just with you. This deep analysis may make you understand whether you are included in his preferences or not!