Component Storage
Purchase the biggest bags you can for your bank slots. Buy as many extra bank slots as you are able to. Organize your bank with all of the profession components in their proper place. If you're a tailor, one bag can be for mageweave, one for runecloth, and another for thread, dye, and other special ingredients. If you keep everything organized, you can gather the components more quickly, create the items, and sell them in the auction house.

Reselling Items
Some players make a profit by buying items that are listed too low and reselling them at their "proper" price. Their profit is the difference between the price they paid for the item and the price they sold it at. This method is for experienced traders only, as you need to really know the prices before attempting this. Sometimes players place an item in the auction house and set a really low price because they don't realize what an item is worth to other players.

Search Options
Memorize a bunch of different search options so you can quickly check what is for sale. Examples:

Select epic quality only and hit search (lists all epics)
Select weapons, level 50-60, check usable items, and hit search (lists all weapons level 50-60 that you can use; you can change the levels)
Repeat the above search with armor selected instead of weapons to list the wearable armor available for your level range
Select recipes and check usable items (shows all available recipes that apply to your professions)
Select recipes, select quality uncommon, and check usable items (shows recipes that are green or better for your profession, if any)
Select trade goods and type in mageweave to list all of the mageweave cloth for sale.
Make a list of these searches and print them out. Then quickly type them in to check all of the items you wish to search for
Use the Number Pad
You can use the number pad on your keyboard to more quickly enter the prices of items as you list in them in the auction house. Make sure your "num lock" key is on. You can also press "tab" to scroll between the price boxes.

Gems
Gems now searchable in the Auction House under the heading of Gem with the gems then broken up by color so you can search for all gems of a specific color.

PDA
You might find a PDA (personal digital assistant) extremely helpful for running an auction house business. You can take notes, read lists, and so on. You can also alt-tab out of the game instead of using a PDA to update your lists. Then there is the classic piece of paper and pen!

Sound
You can hit control-s to disable the sound effects if someone is making really annoying sounds in the auction house. Don't forget to re-enable them after you leave.

Auction House Campers
Some players do nothing but sit at the auction house and buy and sell items. It can be a lot of fun because buying and selling items is a fun alternative to fighting.