Have an interesting expression
You cant go wrong with smiling! Maybe smiling for the camera or camera phone, as the case might be makes you feel a little silly, but taking a random photo of yourself with your phone is a silly enough action in itself. If youre on the serious side, a cool, collected expression could also go over well.
You can play around with different smiles, of course. A closed mouth coy smile can be just as appropriate and just as flattering as a wide, laughing grin. No matter what, a smile is one of the most appreciated and charming expressions you can wear.
It can be hard to make sure your expression looks authentic. One way to make it look more real is to try to capture yourself when youre feeling an emotion. Try taking a selfie while youre watching a movie thats making you genuinely laugh, or right after you find out some shocking news.