MEETING WOMEN ONLINE and through dating appscan feel a bit dodgy in the day and age of “catfishing”—especially now that people have become surprisingly adept at altering how they look in photos. (Oh, the magic of lighting, good angles, and Photoshop.)

Still, there’s a reason photo-based dating apps like Tinder are so popular: Humans like to judge whether or not we’re attracted to someone at first glance, and that means people reveal a lot about themselves—even if they don’t intend to—with their personal dating profile.

Of course that doesn’t mean we’re not immune to dating app traps. Those skimpy, night-on-the-town pics and the racy glamor shots you see? They’re classic ways to catch guys hook, line, and sinker.

But what do these pictures really tell you about her? We asked online dating expert Julie Spira to weigh in on what her sexy selfies and even sexier beach-bod shots reveal. And while we would never call these hard-and-fast rules—take them with a grain of salt, OK?—they’re certainly useful guidelines for reading between the lines of her Tinder profile.

What it means if: She’s selected a sexy selfie

If her main pic happens to be a sultry, look-at-me selfie, Spira suggests flipping through her other pictures to make sure they’re not all the same. One selfie is fine, but a parade of them is a red flag for a high-maintenance narcissist.

Interestingly enough, while women probably take more selfies on average, men are more likely to use a selfie as their main profile picture than women, Spira says. That’s not always a good idea: “Selfies aren’t that flattering—they’re usually not your best photo,” Spira adds.

In fact, on some apps, a selfie can deter people from swiping or “liking.” Instead, choose these types of photos to get the most interaction. (Hint: Half-naked beach photos are out, and black-and-white pics are in.)