the advice about accessories is a great one. I would try and steer clear of the all black pref dress as a rushee but if you find something cute thats like black/white or another color with black try and spice it up with some silver jewlery......
Again, its not just what you were but the confidence you wear it with. Ever noticed the girl everyone pays attention to in a room or is the "best looking" is not always the prettiest or best dressed she just has a confidence that she knows she looks good and it radiates from her