Enchanting is one of the biggest money-makers in the game. Most of that money is earned by selling scrolls, which are simply enchants saved on a vellum. I've written about selling these before, but it was a long time ago and the tools have changed considerably. Making gold with enchanting is surprisingly straightforward and involves three steps: getting mats, crafting scrolls, and posting them.
Let's start at the beginning
Which enchants do you sell? Assuming you're already 525, you'll definitely want to consider all the Cataclysm enchants. The ones used in leveling are almost always going to be cheaper than the mats, but the rest of them may be profitable, especially the ones that you have to buy off the vendor. It's probably worth investing in the new bracer enchants; however, bear in mind that these are somewhat rare BOE random drops that might cost you a fair bit.
Additionally, you might want to sell enchants that are appealing to people looking to enhance their BOA gear, as well as maybe Wrath of the Lich King enchants. Here's a master list put together by Valdron of The Consortium forums that will contain all the recipes generally found to be profitable, at least somewhere. The decision of which types of scrolls to make should be based on whether you have the time to accumulate all the needed recipes and whether you're willing and able to keep tabs on a completely different set of mats. Infinite Dust, for example, is going for 8g each on my realm these days, but there are apparently a few Wrath-era recipes that are still being used consistently. Agility to gloves is the only one I know best as a hunter, but there is a list of all the profitable enchants here that you can trawl for.
All the work you do before you start
Managing mats is probably the most time-consuming part of any crafting business, and enchanting is no exception. The more sets of enchants you're willing to craft, the more mats you have to manage.
You need to know whether you can make them out of something farmable, whether they're produced as a by-product of people leveling through specific content, or whether they're simply so rare that they're basically unfarmable. It's the most time-consuming and (to me, at least) least interesting part of crafting. That's why I limit myself to Cataclysm enchants; the mats are always on the auction house and happen to be a byproduct of jewelcrafting, another trade skill I happen to do a fair bit of.
You'll want to have a way of saving searches so you can check prices more efficiently. The default UI is still pretty much useless to us, so you'll need to use an addon. TradeSkillMaster now supports something like this as part of the Shopping module, although I haven't tested it yet. I still use Auctionator's borderline perfect saved lists and categories feature.
The easy part
Once you have your list and your supplies, the rest is pretty simple: Craft and sell your scrolls. While it's possible to use a wide variety of addons for this, the one that does everything you need is TSM. Configure it to only queue scrolls you want to sell and automatically list everything you've crafted. Once you have a basic idea about which of your scrolls sell the best, consider increasing the quantity you keep in the AH to better meet demand.
I find that it's worth running an extra cancel / relist / craft cycle on heavy raid nights or weekends, but that depends completely on your competition.
Other than making scrolls, you can make and sell Horde and Alliance mini-pets and disenchant cheaply sourced gear for mats. Those pets are occasional sellers, but now that Maelstrom Crystals are nowhere near as rare as they were in the beginning of the expansion, more people are finding them within their budget. If you're willing and able to do the cross-faction arbitrage needed to get the other faction's pet available in your AH, you can probably charge a fair bit more than the one that every other enchanter can make. Still, that's either risky or expensive, and it's always time-consuming.
As for disenchanting, most AH addons include some sort of filter that will let you buy gear that will disenchant into mats worth more than you paid. I don't use them, but I hear that this is still a viable strategy. More commonly, you can find times when some enchanting mats are worth more than the mats needed to make gear that disenchants into it. For example: While ore is expensive now on my realm, at one point, it was 20g a stack in any quantity you wanted. Heavenly Shards were 70g, and you could disenchant them from blue-quality armor made with blacksmithing.
If the price or ore, cloth, or leather goes low enough, you might be able to make gear to disenchant profitably.
Maximize your profits with more advice from Gold Capped. Do you have questions about selling, reselling, and building your financial empire on the auction house? Fox and Basil are taking your questions at firstname.lastname@example.org and email@example.com.