Most Helpful Guy
Generic answer, they look for confidence and assertivity and a guy who has plans and goals and thrives to get what he wants and is taller by at least 4 inches.
Generic reasoning, the douchebags represent something "out of the ordinary" and therefore less predictable and therefore "fun", while also being confident regarding their own viewpoints.
But the truth is, culture defines what they think they should like, they start looking for an image of perfection, then apply it to anyone who seems to have at least a few of those qualities via the halo effect, and want to get the attention and EARN it and not just sit there and get it for nothing, because something you get freely does not hold as much value as what you have to work for.
Not to mention that in high school, usually the douchebags hold social worth, and there are various girls who like being popular and being with the most popular guy. That truly doesn't apply to everyone, though.