It's scientifically proven that people find these thirteen things very attractive.
Smile more if you're female
Much of the science of attraction is rooted in biology—and who we think would make a good mate to reproduce with. So, how to be more attractive is tapping into what the opposite sex (if you're heterosexual) is looking for. Smiling in women was shown in a University of British Columbia study to be more attractive than other expressions; but the same didn't hold true for men. "People typically associate expressions of happiness with femininity," says Alec Beall, PhD, a UBC psychologist and one of the authors of the study.
Wear red
What are some associations we have with the color red? Passion, roses, heat, and...sex. For this very reason, science has shown that wearing red is one way how to look more attractive. "This red-attractiveness link is partially explained by men's perceptions of implied sexual receptivity among women wearing reddish garb," Dr. Beall says. "In 2013, my colleagues and I even noted this effect among a small-scale society in Burkina Faso, West Africa, suggesting that men's attraction to red is a cultural universal."
Don't play hard to get
Women might think they appear more attractive if they keep their partner guessing as to how they really feel—and some research does support this (one study from China found that playing hard to get kept men's interest only after they had chosen a prospective partner). But a more recent study from Germany suggests that people are more likely to rate others as attractive if they can easily understand the emotions they're displaying. The reason for this is in the brain: How well the study participants could decode the other's "neural vocabulary."
Speak in a higher pitched voice for women, lower for men
Ladies, think that smoky voice sounds sexy? You might want to think again. Research from the U.K. has found that a higher-pitched voice in women is more attractive to men—and vice versa, that a lower-pitched voice in men is more attractive to women. "Past work suggests a higher voice pitch is perceived as coming from someone who is physically smaller in terms of body size," Dr. Beall says. "Gender dimorphic—in other words, typically feminine—qualities such as these have been shown to increase men's sexual attraction to women." The opposite would hold true for women, who evolutionarily seek out male mates who are larger in size, signaled by a low voice.
Have a sense of humor
"He makes me laugh," is one of the reasons women often say they find their mate attractive. A sense of humor in a man has been scientifically proven to draw the attention of women. "Studies have found that both women and men list 'a sense of humor' as a highly desirable trait in a potential romantic partner," Dr. Beall says. "But other studies have found that only women actually rate a funnier man as more desirable—women's desirability was less affected by how funny they actually were." This means women want men who make them laugh, but men want women to laugh at their jokes. "Some have argued that women's particularly pronounced attraction to funnier men is deeply rooted in our evolutionary past," Dr. Beall says.
Get a dog
Pets are instant conversation-starters, and who doesn't love a cute puppy? So it's not surprising that researchers from France found that women were three times more likely to give their number to a dude with a dog as one without. Evolutionarily, "women tend to allocate more resources to child rearing, while men devote more time and energy to mating," Hal Herzog, PhD, a psychology professor at West Carolina University and an expert in human-animal interactions, wrote on Psychology Today. So, "women should be more sensitive than men to how their dates treat their own dogs and cats. Men, on the other hand, should be more likely to use their pets to attract sexual partners."
Be kind
When it comes to attraction, it's definitely not all about looks. As in the Gwyneth Paltrow movie Shallow Hal, good people often seem more attractive. "The 'halo effect' suggests that those who are perceived as physically attractive are also perceived as having socially favorable personality traits like kindness," Dr. Beall says. "Interestingly, recent research suggests that this stereotype may also work in the opposite direction—socially favorable personality traits may also affect ratings of physical attractiveness." One study from China asked three groups of people to look at pictures of faces and rate their attractiveness. The group given positive personality info on the faces (the others were given negative or no info) rated the faces as more attractive.
Groom yourself
This one seems like a no-brainer: If you are looking for a partner, it's best not to look like a slob. You probably "clean up good," right? There are biological reasons for this. "Research shows a large part of physical attraction is centered on the more changeable aspects of our self-presentation," says psychologist Jeremy Nicholson, MSW, PhD, who writes The Attraction Doctor blog on Psychology Today. "Specifically, the most attractive physical features fall under 'self-care'—things like good grooming, clean hair, nice fitting and quality clothing, good posture, and healthy weight."
Stop stressing
Just like how smiling and displaying kindness make you more attractive, showing signs of stress, like bags under your eyes or dull skin, makes you less attractive. And not just because stress tends to show up on our faces—somehow, others can sense that it's part of a weakened immune system. In a study from Europe and South Africa, women rated men as more attractive when the men had lower levels of the stress hormone cortisol and a stronger immune system. "Women seem to be able to detect the men who've got the strongest immune response, and they seem to find them the most attractive," study author Fhionna R. Moore, PhD, a psychologist at Abertay University in Scotland, told CNN.
Grow a beard
Biologically, heterosexuals look for typically male or female traits in the opposite sex—the most glaring of which for women is men's facial hair. "The research indicates some sex-specific characteristics are attractive—particularly those that highlight differences between males and females," Dr. Nicholson says. "For example, different styles of facial stubble and beards can signal a man's masculinity." A recent study from Australia found that women considered men with heavily stubble the most attractive—but interestingly, rated men with full beards as the highest for parenting ability and healthiness. Although a beard's connection with health seems random, it actually may be true: Beards are able to block the sun's rays, so they might protect against skin cancer.
Show off your curves
Women tend to think men prefer thin figures—but the opposite might actually be true. According to research, men prefer a waist-to-hips ratio of 7:10, which means you're fairly curvy and have "good childbearing hips." Biologically, men might be onto something: Women with this waist-to-hip ratio have been shown to have optimal levels of estrogen, and are less prone to cardiovascular disease and diabetes. You can play up your hips by walking with a "swaying gait"—researchers at Texas A&M University found that this swinging motion was seen to be extra-feminine to men.
Don't wear too much makeup
This one seems a bit counter intuitive: Aren't red lips a draw for men? Yes, but only to a degree—in fact, women think men like a lot more makeup than they actually do, according to a U.K. study. "Women tailor their cosmetics use to an inaccurate perception of others' preferences," the study authors wrote. Another study also showed that the amount of makeup women wear can impact others' impressions.
Hang out with friends
Due to the "cheerleader effect" (coined by How I Met Your Mother's Barney Stinson) people appear more attractive when they're in a group. But Barney's observation is actually based in science. Research from the University of California showed that study participants rated pictures of people in a group as more attractive than people alone. This is because we tend to "average out" faces in a group, making less attractive members more so. But why would we want an average face? "Typical or average facial features have been shown to be initially attractive and appealing to potential partners," Dr. Nicholson says. A study from Spain showed that men actually prefer women with facial "averageness"—how closely the size, color, and shapes of face resembles other faces in a population.