Earth girls look good (from the back, and 100 ft away).
One thing I have definitely noticed is that almost every female looks good from the back. Especially if you are a good distance away (let's say, 100 feet).
Long hair helps too. From that distance, every girl could be the girl of your dreams. So you walk a little faster to see if you can catch up, and when you do, you shoot a furtive glance to the side to confirm (or deny) your suspicions.
Usually, I am denied.