While I struggle with plain ways to explain horribly complicated photographic problems, I'll offer some simple suggestions for the next few days.
Where to crop
Don't crop (in camera or afterward) people or animals at a joint (elbow, knee, ankle, etc.). If a crop is at a joint, it makes subjects look like they're missing body parts.
Instead, crop into straight portions of limbs or the body.
While we're on the topic, crop mid-pelvis on frontal views instead of near the top of the thigh. Trust me on this one. It will only make the PJ's life easier.
Lastly, since we also tend to make ultra-tight face shots, crop slightly above the hair line on folks with hair. For those folks like me, crop mid-forehead to spare them the shiny results of stress and too much testosterone.
Enough for now,