Full locks keep a guy’s eyes planted on you. He can’t help himself: Thick, bouncy hair is a sign of youth and good health, says anthropologist Helen Fisher, PhD. And men are subconsciously drawn to those qualities because they signal fertility. But don’t use three cans of hair spray to pump things up. “Guys are attracted to styles they can run their fingers through,” says Normant. Just work mousse (like Paul Mitchell Sculpting Foam, $7.95) into damp hair before blow-drying. Use a large-barrel curling iron to create waves, part hair down the middle to give the look a slight edge...and then start taking numbers.