The biggest clue to total dislike is indifference and the clue that I like someone is intense emotion of many different kinds.
Bunny12

Bunny Rabbits cute and fuzzy they want to love you but they have razor sharp teeth - don't piss them off! I'd have to say the amount of attention they pay you, pretty much as Bunny said. If they make excuses not to see you or go out of their way to avoid you, they're just not that into you ... damn movie quotes ... But if they notice you and remember things about you that are beyond the normal ... I'd say they're into you.
It depends in what situation you are. If your in club trying to grab his/her attention and he/she dosnt look at you while you are talking you are waisting your time and theirs.
More Specific Fritzies?
What I really hate is sarcasism. They could use it if they dislike you or if they are trying to flirt with you.
I don't have time to dislike people.
I am highly intuitive, I can normally tell a person's attitude toward me as soon as I enter a room
Body language and eye contact will normally give an indication. A person will only engage in eye contact if they have an interest in you. Closed body language such as folded arms is an indication that they don't . Its not quite black and white though.