The key to looking good in photos? It's all about your jaw, as photographer Peter Hurley explains in this video. Essentially, stretch your forehead forward and down a bit to accentuate your jawline.
It's a long video (15 minutes), but it's full of examples that clearly illustrate how to position yourself and your head. Scrub to around the seven-minute mark for the photo examples, including this very convincing one (posted by Redditor 0xFFFFF):
The tip to stick out your forehead is an update to Hurley's previous advice to stick your chin out (and squint slightly) for better portrait shots (because it's really chin out and down, but even then he says you can get weird things going on with the chin). Remember to do this when you're laughing in photos too, to avoid the natural tendency to bring your head back and create a double chin.
Check out more tips for looking better in photos, including how to become more comfortable in front of the camera, or share your own in the comments.