I cannot answer this from the view of somebody who doesn't like me (because i don't want to assume things, the reason is some people who had bad days act bad on others and it doesn't mean they don't like them, they're just having a bad day) , but instead i'll answer it from my own view when I don't like someone.
Not enthusiastic when interacting. Such as wanting a conversation to end right then right now. Won't ask further about the topic and just end it with 'ah'
Will not look straight into the eyes. This is quite powerful because you know someone is being interested if they look at you eye to eye when speaking.
Will change mood. Look so happy but then you talk to them they will look irritated.
Will not initiate a conversation. Ever. Unless they had to.