It is important that you understand him and what he is really like, try not to make it haraam as the shaitaan whispers in your ear while you are alone with a male or a female so brothers and sister take in mind that choosing your own oposite sex is not haraam or wrong just try and make sure that you do nothing sill before marriage even if you know no one is watching remember that our god (SWA) is always there!...don't let yourself down and go tell the person that you love them so that you may get married.
Liking someone is the most Islamic act. Allah's teaching in Islam forbids you to hate or dislike anyone. Love for all hatred for none! But for a girl to like a boy before marriage, choosing him as the intended life partner, or vice versa, is not wrong, nor haram. It is a sensitive matter that this liking be conveyed somehow to parents, and let them decide about it. Everyone has the Islamic right to choose his/her life partner.
Absolutely not, you should like everyone until you have reason to do otherwise.