Knowing how to tell if a gay guy likes you isn't an easy task. It depends on his individual personality and his sexual orientation. He may be open about his sexual orientation or he may not be. Either way, you can't be sure until he reveals it to you. However, there are some signs that you can look for to get an idea of where he stands on his sexual orientation.
For example, he might compliment other men frequently and he might be extremely affectionate with his male friends. He could also become uncomfortable if you bring up homosexuality or gay people. He may even become homophobic. He may say things like, "I hate gay people" or he may be snappy and rude when you discuss homosexuality. These are all signs that he is at least bisexual or homosexual.
Another thing to look for is if he has a close group of gay friends. If he hangs out with them and you can't remember him ever dating a girl, then it is a good sign that he is gay or bisexual.
Having a close group of gay or bisexual friends is one of the most obvious signs that he is gay or bisexual. He probably doesn't want to reveal that he is gay to you yet, so it is best to keep it private for now. However, if you are comfortable with it, you can ask him outright if he is gay or not. This can be done by playing a game of Truth or Dare. However, it is best to play this with a close group of friends so that it doesn't seem awkward for him.