In the bottom left corner of the trade interface when you want to Buy Cheap WOW Gold, there is an area filled with Cheap WOW Gold where you can select how many of a specific item or Cheapest WOW Gold you want to create. This is very helpful when you're creating the same item and WOW Gold repeatedly. There is also a "Create All" button that will create as many copies of the item as you can Buy WOW Gold.
Tips
Buy stacks of Profession components from other players who want wow money. That is faster than collecting them on your own! Have your friends save up components too.
Devote a certain bag to carrying your Profession items and World of Warcraft Gold. You can even pick a different-colored bag if you have one, to make it easier to find Cheap WOW Gold.
Know which classes will need the products purchased with WOW Gold that you can create with your Professions:
Mail: Warriors, Paladins (Hunters and Shaman can start wearing mail at level 40)
Leather: Rogues, Hunters, Druids, Shamans
Cloth: Mages, Priests, Warlocks
Know which Profession components to save while you are fighting for wow money. You can sell them to other players or give them to friends who intend to Buy WOW Gold, rather than selling them to the merchants:
Blacksmithing: jewels, metal bars, linen, wool, leather...
Engineering: jewels, cloth, leather, mechanical items, metal bars...
Leatherworking: leather, ruined pelts, hides...
Tailoring: linen, cloth, wool, silk...
Cooking: meat, various monster parts...