Everyone who plays World of Warcraft is always looking for ways to make more gold. Thanks to resources like the Warcraft Riches guide, these tactics are made available and can be used over and over again without any fear of a WoW account being banned. Check out this tip for using a Mage to make some easy gold in World of Warcraft.
One tactic for higher level characters is Area of Effect (AoE) grinding. This involves using a character class, usually a mage, and getting a lot of mobs to gather around the character before unleashing a bunch of spells or attacks that will take out the entire group in short order. The trick to AoE grinding is to make sure that the amount of time and resources to take out the groups couldn't be better spent taking out mobs one by one. Keep in mind that you'll probably need to sit and eat or drink to recover before taking on the next mob.
One good place to do AoE grinding is Silithus. There are many humanoid mobs in this area. Usually humanoid mobs tend to drop better stuff when killed, so being able to take out large mobs of humanoids in a short amount of time can help bring in a good amount of gold. The humanoids in Silithus have a tendency to drop runecloth, which can sell for a decent price at the Auction House. Once you've cleared a few groups, head back to the Auction House and sell off the stuff that dropped that you don't need. You'll probably also get some good coin drops from these mobs too. There might be some stuff that you can sell to a vendor and get a decent price for as well.