Much like Enchanting, Tailoring is a Profession mostly useful to people that wear cloth, namely Mages, Priests, and Warlocks. With Tailoring, you can craft your own gear, and it tends to be reasonably reliable at any given level if you pick up the skill early enough. It also lets you craft bags, which is worth it for many people on its own.
Thankfully, Tailoring is one of the easiest skills to pick up early, depending on your race and faction.
World of Warcraft Classic professions: How to get started as a tailor
The Horde has it especially easy. Trolls and Orcs practically bump into a Tailoring Trainer after leaving the Valley of Trials (at the Crossroads in the Barrens), and Tauren has a similarly easy trainer to sign up with right after leaving their starting area as well. Undead even have one in the Tirisfal Glades, their own starting area. Plus, of course, the requisite trainers of all types in each race’s capital city.
If you go Alliance, it’s a little bit harder for some races. The easiest trainers to locate are in the capital cities of Stormwind, Ironforge, and Darnassus. This is a bit of a walk for Gnomes, Dwarves, and Night Elves, though a quick hop and a step for Humans.
Finding the trainer is just the first step, of course. To make any Tailoring recipes, you’ll need cloth, which drops from humanoid enemies, as well as some variants of Undead and other enemy types. Thankfully humanoids are abundant in most zones and include anything with two legs and two arms., including monsters you wouldn’t necessarily expect (like Murlocs). Killing stuff roughly on your level in whatever zone you happen to be in yields a pretty solid supply, and routes can be charted through many zones to maximize farming efficiency if you’re into that.
You’ll also typically need a thread of some kind; this may be purchased from Tailoring suppliers.
The most basic type of cloth is Linen, and the most basic usable unit for making anything is a bolt of cloth (Linen to start), which is crafted from two cloths of some kind in your Tailoring menu (accessed by pressing the skill icon in the General tab of your Spellbook). Making the cloth itself is guaranteed to give you a level per bolt for quite a while and continues to be a good source of levels through much of the game, though you’ll need to upgrade what type of Cloth bolt you’re making as your skill progresses and Linen eventually stops giving you Tailoring experience. Typically Bolts of line Cloth will get you up to about level 50, and then you’ll need to swap to whatever the most efficient recipe you currently have is up to the next threshold, where the new Bolt of X Cloth will get you another 30-ish level before tapping out.
With this in mind, you can become a master Tailor in no time flat! Or at least be good enough to make bags to carry around all those materials.