Whether you are shooting portraiture or an engagement couple, it is important to be mindful where you should and should not crop a person. The most basic fundamental to remember is simply to not crop at the joint like the elbows, wrists, or knees. It is better to crop just above or below the joints.
Digital Camera World has an easy-to-follow visual guide that illustrates this basic cropping rule with the infographic below. Areas where you can crop are marked in green, while areas where you should not crop are marked in red. Simple, right?
(Note: The only lines I would switch here are the thighs and the knees. I would crop at the thighs, but not the knees)
Finally, if you are shooting a couple and there is a height difference between the two, you can have the taller of the two stand in a wider “A” stance to minimize that height difference.
Image courtesy of DigitalCameraWorld.com
Thanks to The Phoblographer for the find!