Your own kind. It will be good if you belong to a group of a few good friends. If you don't, try to find one. Reason being: a) You'll have people to laugh with or complain to.  b) You'll have people to eat and drink coffee with.  c) It is a social identity and a major deterrent to bullies! 

        When mixing around, try not to be too flamboyant in befriending everyone. Remember to be sincere and approachable and DON"T make a nuisance of yourself! Read the situation and make people like you. (Just be yourself and be nice) Golden rule: Never "pose" or "act cool!" 

        When mixing with the opposite sex...hmm...just be more conscious of your stupid or silly gestures and appear a bit nicer than usual (Hey! The whole world is doing that!) Bottom line is, again, be yourself. Don't pretend to be someone you're not. If you have a nice personality, your personal happiness will blossom in no time!

P.s. The Halls are great venues in getting acquaintances!