Everytime i have an item on AH and i get the " A buyer has been found for your auction of Ghost Iron Ore (or whatever item it is)" I go look at the Auction House under my autions and check the guy that bought my mats or whatevers name, then I shoot him a message, or if hes offline, I just send a mail to him/her. I'ts alwasy a good idea to do this, because you can find alot potential buyers, mostly theese guys buys bulk, and you'll emty your bag from ores or herbs in a matter of minutes.
This is mainly how i get all my mats sold fast, after ive botted loads of ores and herbs, i list some of them on AH, and then i keep the rest in my bags or guildbank or whatever, and then i wait for my auctions to get sold, after that its time to /w the buyer and ask him if he needs more.
Sometimes they become your personal buyer, that buys everything you have.
Depends on the demand, and on your luck.
Common sense probally, but its still smart and many people don't think of this.
Enjoy!