Hands are a nightmare for most artist...myself included. It's hard to contruct it in basic shapes so I don't really try. Instead I break it up into major forms and really pay attention to where it folds and bends. MAKE SURE YOU HAVE READ THE FIRST HAND TUTORIAL! This one doesn't deal with proportions like the other did. This is more the form of the hand.

The hand is kinda like a shovel...that's what we use it for somtimes. You're palm gives you the lines you need to see were it bends. Above the top blue line is the first row of knuckles.

Don't make the hand a flat wedge. It curves and follows the contours of the lines on the palm. Notice how the thumb side of the palm pivots from the center.

even when drawing the hand from the back..pay attention to the fold lines in the palm. It will help you draw more natural positions for the thumb and fingers.

Below is a series of hand studies I drew based on the above diagrams. I kept some of my stucture lines in tact so you could see what I was thinking when I drew them