I'm actually very good at it, i'd rate myself 90%.
For example there is this reallyc ute boy in my Civics class and he comes off as being homophobic and is just very rude, but every now and then i'll turn around and see him stare at me. Then there was one time where he stood right in front of me and fixed his pants and me being myself just looked down there and saw a *****, it wasn't hard, but yes it was a nice one.

, but then I looked up and he smirked at me and walked off that was one of the signs. There was another time where I was gulping down my water and he was talking to his friends and saying "That Ni**a a Pro, look at him deep throat that water bottle" and laughing trying to make it seem as if he were joking, but I knew the deal. Then third strike was when he sat down behind me in class and asked me to help him with his work while rubbing my shoulder, what straight guy does that? I'm still waiting to get him by himself tho *suspicious smile*. One more instance was where he was looking at this Girls ass and this other girls asked him if he would "tap those", he said "No, I would eat them." What straight guy openly admits that he eats ass?
And then there is also the mental aspect:
There is this other guy whom I've never talked too or really observe, but for some reason my "gaydar" always goes off when I see him. I don't know what it is, he doesn't act fem., dress in a :gay" way, or hang with a whole bunch of girls, or anything I just get this strong feeling that he is gay. He is cute, but i'm not really attracted to him.