12 Principles of Animation -
This action adds to and enriches the main action and adds more dimension to the character animation, supplementing and/or re-enforcing the main action. Example: A character is angrily walking toward another character. The walk is forceful, aggressive, and forward leaning. The leg action is just short of a stomping walk. The secondary action is a few strong gestures of the arms working with the walk. Also, the possibility of dialogue being delivered at the same time with tilts and turns of the head to accentuate the walk and dialogue, but not so much as to distract from the walk action. All of these actions should work together in support of one another. Think of the walk as the primary action and arm swings, head bounce and all other actions of the body as secondary or supporting action.
Program - Maya 2010 http://www.autodesk.com/products/maya/overview
Rig - Goon Rig http://www.kennyroy.com/public/How-to-Cheat-in-Maya-2013.cfm
Character Animation Crash Course -
Illusion of Life -
Animator's Survival Kit -