When you look at an unmodified enchanting tradeskill window, you'll see first a bunch of scrolls that don't sell (since they're from other expansions), have no idea whether they can be sold at a profit, and have no idea whether you've already made a batch and listed it for sale. Also, while I wouldn't consider this a core required function, if you do decide to make a batch of scrolls, there's no way to queue them up and see what the total materials needed will be.
The first and best answer to these problems is TradeSkillMaster. I linked Olivia's excellent guide to starting off, and the download instructions are in that post. Once you get to the part where you're choosing which items to craft, come back here!
First of all, the best scrolls can only be made if you've gotten enough reputation with the August Celestials and the Shado-Pan. If you can make these, you absolutely should. They sell very well, and are typically more profitable than the other scrolls because nobody sells these at a loss while leveling enchanting and not all enchanters can make them.
Second on the list are the non-reputation gated scrolls you can learn from the trainers. You'll want to put a tick-mark next to any enchant that says "requires a level 372 or higher item", although you want to be sure that you don't blindly craft them all. Many of these will never be sellable at a profit because they're the cheapest way to level enchanting. In any case, you want to see them all when you look at your tradeskill window, so check them all.
This is my sweet spot: a single expansion's worth of material types, no oddball reagents, and constant demand. Even the enchants that aren't best in slot for anyone will sell, as sometimes people will choose a cheaper enchant that's not completely useless over having an unenchanted item.
Lastly, you have the oddball enchants. If you can enchant BoA gear (anything without a level requirement), you will be able to make all kinds of gold. The problem is that the BoA enchants market will require you to manage many more types of dust, essences, shards, and crystals than you'll have at the latest tier. Also, a lot of the old popular enchants have stupidly hard to find non-enchanting materials that are a real pain to watch the AH for (or worse, farm for). If you want to get into this market, I'd recommend reading the Consortium enchanting list's section on BoA enchants.
Now that you have TSM set up, all you need to do is create a queue for yourself, acquire the materials, craft your scrolls, and list them for sale. The first thing you should know about getting materials is that they're not worth what you paid for them, they're worth what you could sell them for. If you can reliably sell Spirit Dust for 2g each, then even if they're costing you 50 silver to make because they're a byproduct of your Jewelcrafting work, they're still worth 2g each.
Next up: the cheapest way to get Mysterious Essences is often to craft them from 5 dusts. The US Alliance average market price on essences is higher than the US Alliance average market price for 5 dust, so it's a safe bet that most of you will be able to do this sometimes. In fact, that's actually a good way to make some simple and easy money: buy cheap dust, craft it up to essences, and sell them at a profit.
For some reason, the market price for Ethereal Shards (78g, on average) tends to be low enough that it's not worth crafting them from Mysterious Essences, but it is worth using them to make Sha Crystals. Unfortunately that last step up to Sha Crystal is on a daily cooldown, so if you can make enchants that require these, you'll almost always need to get some from the AH.
There is no way to craft epic gear for less than the average price of a Sha Crystal that I've heard of, but there are many ways to craft lesser gear to profitably disenchant. Jewelcrafting is still the largest source of these, with the green and blue jewelery from the uncommon gems, as well as the 450 blue jewelery you can make from Serpent's Eyes. There are low level greens you can make with other professions, but with the recent nerf to ore drop rates, the blacksmithing one isn't worth it any more, and with the average price of Windwool being so high on average, the Tailoring one wasn't ever worth it.
Maximize your profits with advice from Gold Capped. Want to know the very best ways to earn 10,000 gold? Top gold making strategies for auctioneers? How about how to reach 1 million gold -- or how one player got there and then gave it all away? Fox and Basil are taking your questions at firstname.lastname@example.org and email@example.com.