older nikkor 28-105 macro lens
I got the same one, images are pretty sharp on it.
The whole cutting heads and other parts deal is this. One can shoot anyway you want and since photography is really a subjective form of art, there is no
RIGHT OR WRONG way of taking an image. There are guidelines for portraits, like not cutting part of the feet, or fingers, etc etc, books you have might talk about it.
There is a book out there, for the life of me I don't remember its name and can't find it on the shelf that describes classical approaches of photographing body parts. See if you can find something like that. The way I was taught by wedding freaks

is during so called learning period, do things straight fwd, once you get a hang on basic&standard junk you start playing around with composition, lighting, exposures, etc etc.
Keep shooting and improving.
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EDIT
Here's a book that I like, though can't find on the shelf now.
Body Parts: Don Blair's Guide to Lighting and Posing
It'll teach you how to cut body parts

(using photography)
This is the image (taken from
http://www.shutterbug.net/images/archivesart/1299books158i09.jpg)
Good luck