Sadly I didn't get to finish my writing over the weekend, but I did crank out another hand sketch.
At first glance I thought this looked OK, and then I started to realize all the things wrong with it. The middle two fingers are way too small for a start, both in length and thickness. It is like I have transplanted babyfingers onto my hand. Not to mention my little finger is nearly the same size as my index finger.
The thumb too is fatter than it should be near the base, and the hand on the opposite side juts out too far or too low for the size of wrist.
Don't even get me started on the shading of this thing. When my piece goes up on drawing hands you will see what I was trying to do (and why it failed so spectacularly).
Hopefully I should be able to shed some light on why these common things happen, and how to try and avoid them in future.