Lvl 55+ needed (you dont need to farm until then anyway )
Get the enchanting profession and get it up to 300 (not required but your income will become a lot higher) once its there, spend some cash and get the good recipies, yea, yea.
Now go into an instance with a lot of bosses, or bosses that have a high drop rate of dropping a blue/purple item(s). While your going through the instance pick up every item thats green or above. Once you get out disenchant ALL of them. Reset instance and keep doing until you have a good stock. Go to the AH and check the general prices on each item. Price it about 1 gold or so lower than the average price. Also at the same time you can be selling fiery/crusader/icy ect. enchants to people to make even more cash. You can make good cash this way because putting the DE materials on the AH costs you no money unlike other items.