My first real introduction to rigging was Javier Salson’a reverse-footlock tutorial.  It’s an interesting technique that results in a fairly easy-to-use foot rig.  What was significant about this tutorial is it introduced me to the idea of using an ik pole vec constraint to control where knees and elbows point.  With this tutorial, I produced my first actually usable rig (a simple carrot, that I animated my first walk cycle on).

I’m not sure if reverse footlock is the best foot rig or not.  Certainly I’ve learned a lot since first being reading this tutorial.  But this is still where I really started to understand rigging for the first time.