Camera angles work wonders, high camera angles look flattering on pretty much everyone!
Also try angling your head certain ways in front of a mirror to see what works and what does not.
I don't know if this goes for everyone but.. I try to avoid having my head straight-on to the camera, this often makes my face look bad complete with a double chin and whatnot. Instead I always turn my head a bit more to the side, often also tilting my head up very slightly while I do so.. not too much though or it will look just as bad. XD
*~Cosplays in progress~*
Masamune Date - Sengoku Basara
Eren Yeager (casual outfit) - Attack on Titan
Sanosuke Harada - Hakuōki: Shinsengumi Kitan