Hands are always a real pain to model and animate convincingly and I don't pretend to be there yet. Often the best trick is to pick a style of animation that does not require a photo realistic look, the more you make your images or motion photo real the more your audience will be intolerant of inaccuracy in your characters and scenes. Having said that... it is always fun to fly that curve as close as you can manage. This hand is made from 508 spline patches and 30 bones (no hooks or Hash five point patches as they hadn't been invented at the time). Bones are placed in reasonably anatomical accurate positions - carpal, metacarpal, proximal phalanx, middle phalanx and distal phalanx (time to reach for that book on anatomy). Two additional bones per finger are placed at the joints to smooth the skin shape during a bend. The mesh at these areas consists of three spline loops with the middle loop attached to the joint bone.
To help simplify animation, Aim Like Two constraints are setup on all finger and thumb bones, between a null target at the tip of each finger and the next bone lower in it's own kinematic chain, ie. distal phalanx bone constrained to null and joint, joint bone constrained to null and middle phalanx, all the way back to the knuckle... All finger bones can then be hidden, and animation achieved just by moving the finger and thumb nulls.
Having played with this model for a while, I've gone through a number of revisions of the constraint setup. Each finger is now a conventional IK chain from the finger tip back to the proximal phalanx. The extra joint bones are again used to smooth the skin over a bend, but this time they use two Orient Like constraints at 100% to the bone on either side of the joint. Make sure the joint bone is not part of the finger IK chain, otherwise your two Orient Likes will generate a circular constraint. Finally the finger bones have a Spherical Constraint set to stop them from bending too much laterally. Try this article for more detail on the model and setup.