In our world there are two groups of people: a) naturally photogenic who look great in every photo no matter what, b) other mere mortals who usually look better in real life. Do not worry, I put myself in the second category but all of this can quickly change.
Probably the main thing to take from this article is to try to look as natural as possible. That's usually easier said than done. Especially if you do not take that many photos of yourself. If you do take quite a few photos, this article could give you some inspiration for your future photoshoots.