How you can tell someone doesn't like you. They will usually be very distant and try and ignore you for however long they can. This might not be the case though. You got to pay attention to how they act, and if it could be, awkward, or usually rude. Some people may dislike you, but don't want to rude about. Others will just plain throw it out there. If you think someone might hate you, then welcome to the club. I'm not your friend, but if you need to talk, I'll listen. I probably understand what you're talking about. On the other hand though, I if it's just a false alarm, then good for you, I'm only here if you need to talk. Not talk about the weather, now don't waste my time.
And guys, seriously don't waste time.