How to flirt...

At a Party

The easiest way to create that unspoken connection with someone is through eye contact. (Yes, there's merit to that whole "and then we locked eyes from across a crowded room" thing.) Try holding a person's gaze for more than a second—most eye contact lasts just a fraction of a second. If he smiles or looks away and then back at you, it's your move.

At Happy Hour

Smiling is a bona fide way to draw someone in, but once there's a bit of banter between you and your target, your facial expression should change frequently, according to a report by the U.K. think tank Social Issues Resource Center. Try raising your eyebrows in surprise, nodding in encouragement, making that cute, quizzical face when something doesn't sound right. Just remember: You're not playing to the back of the house—keep your expressions natural, not overly exaggerated.

Out Shopping

According to a 2012 study, women who flirted got a better deal when negotiating than friendly women did. While the friendly gals were seen as pushovers, study author Laura Kray, PhD, said that "flirtation conveys assertiveness and power, from someone who is also concerned about satisfying their own interests."

The next time you're haggling over the price of something, here are three key strategies from the study: Smile, appraise (with a quick up-and-down look) and touch his arm. (Avoid the hand, which is waaay more personal.)

At Work

Depending on your office environment, different degrees of flirting will be okay, while others could ring sexual harassment alarm bells. When you're negotiating in a work setting, the safest techniques to try may still be physical, but don't involve touching. That means make eye contact, be mindful of your expressions and try mirroring the other person's body language. If he's leaning forward and resting an arm on the table, then go ahead and do the same.

At the Post Office

If you've been waiting in line anywhere—whether at the post office, airport or (gulp) the DMV—the person helping you is probably as disgruntled as you are. To change the mood, try using the person's name. (Hopefully they'll be wearing a name tag.) It will disarm them and create a sense of warmth that you can build on.

At the Gym

If a guy looks really into his sets (you'll know by the grunts and groans he's making), steer clear. It's best to wait until someone has put down the weights or dismounted the treadmill before making a move. Like at a party, lead with eye contact to gauge his interest before going in.

With Another Woman

A subtle flirtation can exist between two women—and not in the bom chicka wah wah way. It's the kind of exchange that usually takes place with someone new, a person you might hope to become friends with. To charm her—without scaring her away—ask her questions that will lead you both to some common ground.

With Your Significant Other

Flirting can help keep your relationship healthy, says Brandi Frisby, professor of communication at the University of Kentucky. According to her research (aptly titled "Without flirting it wouldn't be a marriage"), couples who flirt with each other are more satisfied and committed in their relationships. So go ahead, give your husband that come-hither look every now and again.