I have a confession to make: I've been playing the AH pretty hard for a few weeks now (ever since I started grinding up to the 5000g for my epic, and yes I got it finally), and I've come up with a lot of good tips for you guys, but I've kept them to myself, because I was selfish and didn't want my sources of gold to dry up. But now, I've got pretty much all the gold I need, and I'm ready to bring these to the world. Lots of you will already know what I'm going to say here (some of you might even be angry that I'm telling everyone), but for those of you who haven't found these little holes in the AH, here you go.
First of all: level up your First Aid to 325 right now, because I've got three words for you: Heavy Netherweave Bandage. Think all that they'll do is heal you? Think again -- they vendor in the game for a whopping 6g per stack, so every time you log on your AH alt, the first thing you should do is run to the Auctioneer and buy up all the Netherweave cloth you can find for less than 3g -- crafted up into bandages, each stack of cloth is worth at least that, so anything you buy for less than 3g (I've seen it as low as 1g 50s -- people are throwing away money) is pure profit. This is the biggest moneymaker I've found (you don't make much per stack, but after you've "processed" a few hundred stacks, the money adds up), and it made me regret selling Netherweave for anything less than 3g before I figured this out.
Second big tip: don't ever buy anything on the weekends. Ever. Prices soar on the weekends, so much so that you'll often be able to take advantage of huge bargains during the week, and then turn around and craft or just resell those items on the weekends, when everyone else is playing. I know you really, really want that Primal Air on Sunday so you can finish off your profession leveling, but wait three days -- by Wednesday, all of the AH sellers will have seen their auctions expired and will be ready to lower the price.