HOW KISSABLE ARE YOU

Ever since Juliet teased Romeo about kissing "by the book," women and men have been striving to do it better. But is smooching really that big a deal? Yes! New scientific research proves it can make or break a relationship.

Here, our three-step guide to unforgettable kissing:

Listen to Your Lips

Sixty-six percent of women have broken off a relationship after a bad first kiss, according to study results from evolutionary psychologist Gordon G. Gallup Jr., Ph.D., at the University at Albany. And that's not shallow: "Kissing is nature's ultimate litmus test," says Sheril Kirshenbaum, author of The Science of Kissing. "Sometimes you can kiss someone you think is ideal, and yet suddenly you feel different. Women are most attracted to the scents of men with a different set of genes."

Keep Practicing

Fun stat: 20 percent of college students have romantically kissed more than 20 people. Once you're settled, keep at it. A study from Lafayette College in Easton, Pennsylvania, found that kissing releases chemicals that reduce the stress hormone cortisol. "Kissing is something that often falls by the wayside when we're with someone for a long time," says Kirshenbaum. "So when you have somebody, keep kissing them, because it's the ultimate way to reconnect."

Make Every Time Like the First Time

In Christina Haag's recent memoir, Come to the Edge, she dishes about her romantic relationship with John F. Kennedy Jr. After practicing fake kissing for a play, the onstage lovers finally really lock lips. Writes Haag: "We sat for a while under the stars and felt no need to speak. But then he did. 'Can I do this for real?' He didn't wait for an answer; he leaned in. Only our lips touched. It was gentle, hands-free, exquisite. I opened my eyes for a second … and saw, by the lines at his eyes, that he was smiling."