Like male peacocks showing off their magnificent plumage to attract a mate, some men on dating sites post topless mirror gym selfies.

Not such a good idea, according to dating experts. Women, they say, tend to swipe left when they see gym selfies.

Likewise, dating sites are full of women's selfies taken from an elevated vantage point, highlighting their cleavage.

"Some women think, 'If I show a sexy picture, he's going to think I'm sexy.' If you show a sexy picture, he's going to want to hook up," says online dating expert Julie Spira, founder of CyberDatingExpert.com.

Her advice instead: "Anything that you wouldn't want your children, your parents or your boss to see, doesn't belong on a dating profile."

So what does make a good photo for dating sites and apps?

The profile photo is the important first impression, and "it should be friendly and approachable" as well as attractive, says Alex Williamson el-Effendi, head of brand for the Austin, Texas-based dating app Bumble , where women make the first move by initiating the chat after a match.

Ideally, the profile photo also should say something about your life: "Good photos show what you're passionate about and show your potential date what life could be like if they were dating you," says Spira.

That doesn't mean including other people in the picture.

"One of the biggest mistakes you can make is your first photo being you and a friend, or you and a group of friends," says el-Effendi.

Shruti Shah, 30, who works in public relations, blogs about food in New York and is on dating apps Hinge and Bumble, concurs. "It's a red flag for me if every single photo is a group photo. It kind of makes me think that he's not comfortable with who he is in being able to stand alone and put himself out there," she says.

Jamie Madnick, 27, a preschool teacher in Philadelphia who met her boyfriend of over a year on OKCupid , says she didn't like seeing "a guy in a picture with a girl or all girls. It's intimidating."

For her own photos, Madnick says she always included "a full body, because I don't want it to be deceiving," and she included travel pictures "because that's a big part of my life. I want to show them if you are going to be with me, expect adventure and expect travel."

Keeping the photos focused on you is important in "creating that attraction," says another online dating expert, Laurie Davis Edwards of eFlirtExpert.com, based in Los Angeles. Don't waste time with images of sunsets or anything else in the brief period of time you have. "If there's one photo that's kind of questionable to them as far as attraction is concerned, they're on to the next person," she says.

Good photos that show you and your life are conversation starters.

"You're giving people prompts and tools they can work with to ask you questions," says Shah.

Oh, and remember to smile.

"I definitely like seeing a guy who's smiling in most of his photos. It just kind of makes me think he is a little bit more approachable and down to earth," says Shah.

Some other photos do's and don'ts from the experts:

Do have images that are well-lit, in focus, and not noisy or grainy.

Do have a close-up of your face as well as a full-length image, so daters can see your body type.

Do use captions to identify family members if they're in your pictures.

Don't use filters, which can be distracting and make you hard to see.

Do allow potential matches to see your eyes. No sunglasses.

Don't be so small in your photos that you can't be seen easily, and don't wear clothing that covers you head to toe, such as a ski outfit.

Don't show yourself drinking in every photo, unless drinking all the time sums up who you are.

Do edit the choice and sequence of your photos; some dating apps auto-load the first handful of images directly from your Facebook account.

Do consider whether you want to have pictures of your children on your dating profile. Yes, you want to let potential matches know if you have kids, but sharing their pictures might be better after you have matched.