The biggest mistake that I see people make with their iPhones is that they stand too close to the person when taking a picture. The problem with this is the closer you are, the more you are distorting the person. When you get closer, you are naturally much closer to one part of their body more than the other.
In this illustration, the camera is closer to her head than the rest of her body. The result will be a big headed woman! Something like this:
That's not what she looks like in real life. Her head isn't that big and her legs aren't that short! This is what she looks like in reality:
Pretty big difference right!? So, how do we correct this? The key is to:
STEP BACK AND ZOOM IN!
To help you with this, choose the 3x zoom and then get back enough to crop the way you want. Do NOT shoot a picture of a human at the .5 zoom. You'll surely get too close and distort and give them self-esteem issues!
The difference may not be that obvious if you only see the distorted image. But here's a side by side comparison. The first one is up close and at .5 zoom, the second one is stepped back and 3x zoom:
The difference is obvious when you compare side by side. The image on the left would make him wonder how his legs got so short and his head so big!
So, next time you're taking a picture of someone with your iPhone, step back and zoom in.