Keybindings: #1-Remove Basic Attack from Action Bar

Right off the bat, I remove the basic Attack or Auto Attack button from my action bar.  Hold shift as you click the spell icon and drag it off.  Dump it anywhere on your screen.  If you dump a spell, it is not gone from the game.  You can open your spellbook (type P or click the book icon on your toolbar), find it, and drag it down to the action bar again.

I remove Attack because I prefer to always right-click on my target when I want to do a basic attack.  The auto-attack kicks in and keeps hitting your enemy even if you don't do another thing.  (You can toggle auto-attack off...later.) What I do is right-click on a target while I am still way out of range.  Nothing will happen until I am in range, whereupon auto-attack starts doing damage.  This helps you get a feel for the range you should be in to engage your enemy.

While all classes have Attack, casters work from range and so shouldn't ever be hitting with a melee weapon.  (Melee weapons for these classes will disappear when Pandaria is released and we'll see if it works to cast a basic spell at that point.)

More spells will appear in your action bar as you train your first few levels.  I almost always more them around so that they form a 1-2-3-4 series in the rotation that I use most.  Out of rotation spells like heals I will put on the 5 if I use them a lot, or on another action bar if not.

At some point, the new spells stop appearing on the bar automatically, and you must place them manually where you want them. It helps if you already know how.