Reiterating what others are saying in this thread.

Loot everything, and sell the vendor crap to vendors.
Anything white quality is usually for trade skills and will AH well.
Green stuff will generally DE for more valuable components on the AH then the green itself.

Have an AH alt, which you mail stuff to; this toon does not leave the auction house/mail area.
Trade stuff to whichever toon is on the same account, so the mail to the mule is instant.

Between your active toons, include Enchanting, Herbalism, Mining and Skinning skills.
I like a slave to be the skinner, because you can macro this, while you cannot macro Herbs/Mining.
All of your toons could be enchanters if you want, you're looking at the DE feature mainly.
I'd personally just have one enchanter as it costs some to level one.

/targetlastenemy
/use Skinning(Master)

Insert your level of skinning into the brackets each time you improve to a new and better skinning skill.

Your main/most active toon should be either Herbalism or Mining because its easier to click from the main window.
If you have a secondary toon/slave with a minimap large enough to view, they can have the other skill.
This way you track both skills at once, but don't miss either.
If the maximizer region makes their mini map too small, you can easily have Herbs/Mining on the active toon.
Just macro... /castsequence Find Herbs, Find Minerals. Can quickly toggle between them.

Gathering skills make you the gold, everyone uses them, most are too lazy to get them themselves.

If you're on RAF, only buy the essential skills while leveling.
For shammies this would probably be Lesser Healing Wave, Lightning Bolt, and basic totems.
Since mana totems won't stack with each other, one shammy would have the highest rank the others probably rank 1.
Once your maximum level, you can train other things over time.