Science is not magic and it steadfastly refuses to be. That's why you can't expect science to come up with the perfect love potion anytime soon, and roofies are really bad. That's why our love lives remain to be super complicated in the foreseeable future.
However, science has narrowed down the list of physical characteristics that men almost universally find attractive in women. Now, keep in mind that not all guys are cut from the same cloth, so the results might be different from man to man, but in general, these truths hold up!
The right waist-to-hip ratio
Boots are made for walking and hips are for childbearing. Science shows that a 7:10 hip-to-waist ratio is the most attractive, since it means a slim woman with great child bearing hips.
A high-pitched voice
Women like men with deep voices, so men naturally like women with high-pitched voices, since they seem younger and more feminine. This all ties into the peak fertility age, which is 21-30 in women.
Finally, something you can do something about! A woman with long, luscious hair will appear younger, healthier and more fertile for men, so keep your hair healthy!
The cliche that men like natural women turns out to be true: research shown that women with less make up appear 40% more attractive than those who wear a lot.
People like happy folks, and women who smile more (and have whiter teeth) are considered more positive and happy, and hence more attractive.
Red encourages attraction in men, that's why those red dresses are so popular with femme fatales and redheads that marry cartoon rabbits.
Men not only like women with long legs, but they also prefer women with long, slender arms.
A woman that is well groomed appears to be able to take care of herself, which is something men like.