Round face You eyebrows can help you achieve the illusion of a longer and thinner face. You need to shape them to have some height and so, they should be arched high in order to create as many vertical lines as you can. Just make sure that you don't make them too rounded, else your entire face will end up looking like a ball!
Elongated face The aim for this face shape is to make it appear shorter and so, your eyebrows must be straight shaped across the face. Go for flat brows. The arches should be minimal and happen three quarter of the way down towards the end of the eyebrow. These are an easy style to maintain.
Square face Since you have strong features, angled brows with a high noticeable arch can balance your face. Go for power eyebrows i.e. leaving your brows thicker (if you don't have naturally thick hair, fill in with a eyebrow pencil that is a shade darker than your hair color). Keep the shape slightly rounded and not very curvy.
Heart-shaped face If you don't do your brows right, your chin will end up looking too pointed. The brow should arch and curve softly to create a very feminine shape. Opt for rounded eyebrows, but make sure you don't have that constantly 'surprised' expression. You can create a high arch for some drama or a low arc for a more natural look.