World of Warcraft Tailoring Specialization
Tailoring Guide
Tailoring allows players to cut and weave various pieces of cloth into armor, bags, shirts, and other cloth items. Tailors can create cloth items for cloth wearing classes: Mages, Warlocks, and Priests. Tailors play an especially important role in guilds because they can create bags for the entire guild. They can also create specialty bags such as Herbalism bags that can increase gathering for the guild. They can learn powerful rare recipes as the highest levels which allow them to create powerful gear useful in raiding. Tailors can create shirts or dress-up items.
Tailors do not require any special equipment to create their items, such as blacksmiths require anvils. Tailors can create items wherever they want, as long as they have the proper required ingredients. Tailoring does not require a gathering profession. Proper ingredients must be gathered from monsters or purchased from other players. If your friends know you're a tailor they also may collect tailoring ingredients for you, provided you let them know exactly what you need.
At the highest tailoring levels you can choose a tailoring specialization. The three areas of specialization are spellcloth, shadowcloth, and primal mooncloth. The benefit of specializing is that when making the respective cloth, you create two pieces of cloth for the same materials and cooldown - doubling your cloth making output. Each type of cloth has a four day cooldown on creation on their own timer. Therefore, once you specialize you can make two cloths for your specialization and one cloth of the other two choices, all on separate cooldowns.
To specialize, you must have at least 350 skill in tailoring. Head over to Shattrath City, where you'll find four master tailors in the southeast part of Lower City. If you're sufficient level and skill, they'll offer a quest for specialization.

You should review the various specialty patterns you can obtain by specializing before you make your decision. Your class and talent build will likely play a role in your decision. Here are some general guidelines for the items you can make with the three specializations:

Spellfire Tailoring - Arcane/Fire damage items, 28-slot enchanting bag (Fire/Arcane Mage)
Shadowweave Tailoring - Frost/Shadow damage items, 28-slot soul shard bag (Frost Mage/Warlock/Shadow Priest)
Primal Mooncloth Tailoring - Healing, 20-slot bag (Holy Priest)
You can still make some of the above items no matter what specialization you choose, however, it will take twice as long to create an item outside your specialization assuming you create all the required cloth yourself. There *are* certain cloth sets that can only be created by those that have a certain specalization. So make sure you research what set you want before picking your specialization. Trading specialty cloth with tailors of other specialties can be much faster and more efficient. In addition, set bonuses of the crafted items may require you to be of a certain specialization to become active. You can now unspecialize in tailoring and then select a new specialization. This is a repeatable choice, but costs gold each time.

Artisan Tailoring is available at the highest level once you have reached level 35. Horde players should head to Tarren Mill. Alliance players go to Timothy Worthington (Theramore Isle, Dustwallow Marsh).
To advance beyond 300 tailoring, Horde players need to speak to Dalinna (near inn at Thrallmar) in Outland. Alliance players need to go upstairs in the Inn at Honor Hold. Both of these are located in Hellfire Peninsula.
Skinning might go well with tailoring, because you can collect leather for recipes.
Additional Tailoring recipes can be found in encoded messages found on the members of the Twilight's Hammer in Silithus.
There are some tailoring quests such as Shadowweave Mask (NIlith Lokrav in the Searing Gorge) or Meilosh in the Timbermaw Hold, when you have a friendly reputation with the Timbermaw.
Some powerful recipes are bind on pickup and only found from high level enemies.
Many factions have reputation-based recipes available for purchase.