Here's something Tony Ryder suggests in his terrific book. (You can buy "The Artists Complete Guide to Figure Drawing" through this site here:
http://www.portraitartist.com/bookst...aitdrawing.htm )
He approaches all drawing first by creating what he calls "the envelope" a straight-line-segment container around the object in question. He suggests carefully checking the angle and length of each of these straight lines (shown here in red). When using this method on hands he likens it to the idea of "drawing the mitten".
When you compare "the envelope" I made around each hand, you can immediately see the differences. First I notice that the overall size of the hand compared to the features of the face is too large, mostly because of the size of the palm. Then you can see other angles that are different and line segments that are not the right length. You can also see that the shapes along the right-most line of the envelope are too lumpy and don't follow the straight line along that side as closely as they do in the reference.