The smile..I like guys with a very mischievious grin, the kind that tells you that there's something more in that head of his that he's letting other people in on. That, and the face has to be somewhat close to proportional.
i look at the person's hair. if i'm there long enough, then their smile. last, the way they act (posture, body language, habits, etc.). sometimes you can DEPICT a person's personality through their looks. i hate it when they're cocky, but hate it more when they're too shy. haha does that make sense???