Controlling the Auction House in WoW boils down to a simple formula (one that can actually be applied to most markets outside of the game as well, but thats a bit off topic) that can be replicated across practically any in-game market you choose to enter. The steps are as follows:

1. Identify the niche you want to control, and the most profitable item within it. This is well and truly server dependent, and will require you to monitor your niche for a week or so to judge what is worth controlling and what isnt. I could write a whole guide on how to judge liquidity in the Auction House but its a bit beyond the scope of this guide.

2. Once you’ve picked your item out, ensure that you have the gold to buy it out and to keep any competitors from driving prices down.

3. Relist the item in small quantities, creating the illusion of scarcity and driving people’s desire to buy while simultaneously inflating the price of the item for increased profits.

4. Pick up the gold from your mailbox.

If you’ve been smart about choosing your niche, then you’re pretty much done at this point. If you had to start things off small, you can start to scale it up by either expanding your niche or going into another one, depending on which is more profitable, and you can keep on scaling up until the next step is to buy a new account just so you can have more gold mules.

If this is less of a daily thing for you and more of a weekly thing, I would recommend putting your items up for 48 hours starting on Saturday morning, and buying out items on Sunday evening after the weekend crowd lists their items at the substantially lower weekday prices. This pattern may vary depending on your server, however.