The auction house is the most important source of gold.
It is by far the best way to make gold in World of Warcraft. It may seem boring at first, but if you think about it the auction house is very similar to the stock market in the real world. If you know what you're doing, have enough gold to get started, and are willing to spend a lot of time researching and learning about different items in the game, it will eventually pay-off.
You must also keep in mind that there is a cap on how much gold you can make using other methods such as farming. If you try to make gold solely from farming, you can only make anywhere from 400 to 1000 gold per hour, while the auction house helps you make thousands of gold per hour.
At first you may need some time to set it up, check in on your investments and read up on the most recent news in the game, but after a couple of weeks you can spend as little as 20 or 30 minutes in the auction house and make thousands of gold a day.
To use the auction house successfully, you need the right tools. This means getting addons for your World of Warcraft UI. Exactly how you set up your auction house UI depends largely on what you prefer, but regardless of your preference you'll find that there are a lot of ways to make gold that don't require you to spend hundreds of hours each week farming.In fact you can even pay other people to farm for you and make money off their work.
There are other options as well. In-game addons
may save you a lot of time and effort. For example, the Tycoon Gold addon
can help an average player make 230% more gold and an advanced player 500%-700% more gold compared to the exact same strategies they would use on their own. The addon is beautiful and has very few bugs.
It has also been updated for Cataclysm.
Another option is the Edge in-game addon that allows you to get the best talent builds and rotations for raiding, leveling and PvP, soloing and glyph selection. The two addons can help you reach the optimal level and become one of the elite players (top 10%) in a short amount of time.