I'm pretty primitive, after all.
I don't use WASD to move much. I use "R" for autorun and I steer with the mouse. Or I click-to-move, because of all the threads about how awesome that is (click to move plus key bound to interact with target)

Button 1: I don't think this does anything, anymore. Might be my earth shield button on the resto, I forget.
Button 2: Hammer of Justice, or Wind Shear. OR something else on my hunter, but nobody cares about hunters.
Button 3: THIS IS WHERE THE ACTION IS! It's my 96969 pally macro (minus consecration), and the FS-LS-LB etc macro on shamans. It also activates all trinkets. Maybe elemental mastery too, I forget.
Button 4: Taunt and Lesser Healing Wave.
Button 5: Consecration and chain lightning and multi-shot. They spam well together.
Button 6: Avenger's shield and thunderstorm and frost trap/freezing arrow. Usually works fine because avenger's shield is on cooldown from the beginning, so if I'm spamming thunderstrorm in an emergency in the middle of a fight I won't waste a cooldown on avenger's shield.
Button 7: Self-buffs that you do before a fight, like Sacred Shield. Might be my Earth Shield button too, I forget.
Button 8: Empty for some reason.
Button 9: More self-buffs that are suited to pre-combat use; water shield and Seal of Right
Button 0: Follow focus.
Button -: Divine plea (i should probably put this somewhere else) and grounding totem.
Button =: Holy Wrath and Earthbind Totem. <--- the second one is just how it's always been since 2004.

I only really like to use 1-5 in combat. So I hit shift and go to my other bars, sometimes.

Shift+2, button 1: The "accept" macro you see around here. Invites everyone, accepts everyone, accepts quests and trades and all that at once.
Shift+2, button 5: Fire nova
Shift+2, button 7: Fire elementals
Shift+2, button 9: Earth elementals.
Shift+2, button 0: Drink water.
Shift+4, button 5: Flametongue weapon, and Righteous Fury.
Shift+3, button 6: summon non-combat pets (on the first press), target them and attach leashes (on the second press).
etc etc up to mount buttons. I don't use /click because it'd require starting over, and as you can see I'm set in my seemingly random ways.

I'm not posting this as an answer, but as a post that raises more questions as you figure out making your way through your own KEYBINDER'S ODYSSEY