Straight Up Sexy

Why Guys Love It: From an evolutionary perspective, guys subconsciously like hair that looks clean and healthy, like Anna Faris's blond locks. "Hair that's in top condition shows that you have a balanced diet and good health — signs of an ideal mate," says biological anthropologist Helen Fisher PhD.

How to Get It: Work a silicone-based straightening serum through damp hair before blow-drying. Clip locks in 4-6 sections depending on how thick your hair is. Then tackle one at a time with a paddle brush and a blow-dryer equipped with a nozzle pointed straight down. Finish with a light shine spray.