You can't be sure and only the individual knows if he or she is gay. If a person decides to tell you they are gay, then you will know for sure. Otherwise, it's none of your business. Well, some guys act a little gay. For a women they are sometimes butch. But you can't tell most people are gay by these things, just some. Others are right next to you on the bus and others in the doctor's office or even the doctor. Don't be afraid. They are just like you and me, they just love someone just like them which, come to think of it, straights do that, too. Some gays/girls flaunt it and some don't, so it would be very hard at times to tell if a person is gay. It's also not fair to the other person to ask if they are gay so you pretty much have to wait until they volunteer that information. Gays come from all walks of life and can be muscular, rough and tough looking, while some gay men can be very effeminate. Women that are gay can be considered beautiful, feminine, but still can be gay, and some women will act like a guy (often referred to as a Butch). If you are in a relationship and are wondering, then the person may be gay or bisexual. Then if this is a concern to you ask, but be warned, if the person isn't gay or bisexual, this remark could end your relationship. I know how this one guy is gay because he tries to talk like a girl all the time, he gets a little too close to other guys, he hates girls, he wears rainbow colors, and he puts mascara on his eyelashes. Well, you might recognize a lesbian by her behavior, clothing, and/or grooming. If a woman looks a lot like a man---man's hair style, mannish clothing---or if she walks and talks like a man or seems romantically attracted to other women, she may well be a lesbian. If she displays none of these signs, she may still be a lesbian, but there is no way to know unless she tells you. You don't always know, sometimes they hide it or they don't act like the stereo type gay. Some gay guys act feminine, for example talking in a high pitched voice or wearing feminine clothing. Some guys can also seem gay, but they aren't. It can be confusing at times. That's where stereotype comes in...If a guy enjoys dressing nice, taking his time to get ready, and just loves being high maintenance does that automatically make him gay? If a girl has short hair, likes sports, and wears baggy clothes (not because she's a lesbian but because its comfy) DOES that make her a lesbian? That is the mistake that people make when it comes to this question. Gay people, AND straight people are all very different. Some gay guys act more fem, some don't. Same goes for gay girls. Sexual orientation doesn't have much to do with the way we look. There is no such a thing as GAYDAR really. Let me ask you this question then... How can you tell if someone is straight? Hmm? Well I hope this is an OK answer. I just want to remind everyone, don't judge based on looks because looks CAN be deceiving.