I hate buying cloth from the AH 99% of the time as it is overpriced like crazy on my realm so i thought i would write a short guide on some of the best places to farm.
In this guide i will explain the best places to farm netherweave, frostweave and embersilk cloth. (Best results on a level 85)
Let's start with netherweave, this is a burning crusade cloth that is rather easy to farm.
The Blood Furnance is one of the best places to farm netherweave, It is a five-man dungeon in hellfire peninsula, Outland. It is rather easy to pull the whole instance and AoE all the mobs, this can be run five times in one hour.
Shadowmoon valley is my second option when doing netherweave but i choose to farm in a spot where most people do not. (Another farming spot in shadowmoon valley exists, i myself do not find it's drop rate to be as good)
The spot we shall be farming is at the entrance to the black temple, the mobs that you will be killing are called Demon hunter trainer's. The best method is to go in a clockwise rotation around the buildings.
Frostweave is farmed in Northrend and is a rather good cloth to be farming as not many others do.
The first spot i shall show you is a rather intense and the damage done to you can be rather high. The cathedral of darkness is located in icecrown and the mobs you shall be killing are called Chosen zealots, the respawn time on these is rather fast and the place is full of them. Pull only one side at a time at first to see how you can cope with these guys.
Utgarde pinnacle (normal) is an amzing place to farm frostweave, This is a five-man dungeon located in Howling Fjord, Northrend. The drop rate is good and you have no chance of anyone else farming here as it is instanced, you will also get some green boe loot that can be turned into infinite dust and used with your frostweave cloth to create frostweave bags.
Embersilk is farmed in Cataclysm zones, i find this rather easy to farm if you have good aoe abilitys.
In deepholm just slightly north of Stonehearth is a spot with a great embersilk per hour ratio. The mob you shall be killing is Stone troggs, The spawn rate is super fast and you can pull as many as you wish tbh as they do not do much damage.
Now this is going to be two methods in one as it is the same location. The first is fishing shipwreck debris in the waters around Tol barad, the cloth per hour is not so good but you also get other things such as leather. The main spot in tol barad is the restless front, the mobs that you will be farming are named restless soldier and infantry.