WoW UI Tutorial - pvptutorial.com

This video is an introduction on the practice of Keybinding abilities in-game. It gives a brief motivation on why to use keybinding and explains many of the useful practices involved in keybinding.

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Sort of redundant, but here's a quality written guide on an approach to Keybinding by Bloodwraith on Tankspot.com, enjoy.

Also, check out this nice addon for ability activation on down-click instead of release:
http://www.wowinterface.com/downloads/info15078-1.0.html