What's the difference between the portrait on the right and the one on the left? For starters, in the right photo, the model is moving his jaw slightly forward, eliminating the multiple-chins effect. He's also slightly bringing his lower eyelids up (a trick called "squinching"), making his gaze a little more soft, yet piercing at the same time.
Notice the differences in these comparisons as well.
Maneuvering your jaw and altering your eyelids aren't the only tricks, though. To learn more about taking a flattering portrait (or selfie) check out the full article by professional photographer, Dan Solomon, on Fast Co.Create.
Just don't go overboard with the selfies, no one needs THAT many pictures of your face, gorgeous though it is.