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Say no to below.
Unless it's Annie Leibovitz behind the lens (and even then we'd think twice), never allow yourself to get photographed from below. It's the most unflattering angle there is, and can make you look pounds heavier. Head-on can work, but it's even better if the camera is slightly above you. Because of the angle, you'll need to look up, which elongates and thins out your neck and torso.