I didn't see this posted anywhere else relevant so I figured I would contribute.
We all know that playing the AH can make you alot of gold but is a real pain in the ass to do, always running auctioneer scans and such every five minutes.
Well, here's an easy way to make gold if you are on a PVE server or have access to more than one account.
Play one faction's AH against the other.
You'll need to make two alts on your server's opposite faction. Send the first to a major city and set his hearth there. Now check the AH for prices of enchanting mats, preferably the big ones like large prismatics and eternal and planar essences. Take note of how these prices compare to the other faction's prices. A mod like Auctioneer helps but is not necessary.
Now run this alt to a neutral AH town. Learn the flight point there. It also helps if you run an alt on your original faction to a neutral AH as well so u don't have to keep running your main back and forth. Sell the Food/Water your toon starts with so they have like 4c apiece or so.
On your main, buy whatever enchanting mats that were priced evenly or favorably; You'll want to buy at least 100g worth but really any amount can work. Mail these to your same faction alt in the neutral town. This mail sends instantly since its between alts, so now log on your same faction alt and post a stack of mats for 1c buyout. Enchanting mats have no deposit so you can get away with this.
Now, immediately switch to your opposite faction alt and buy the 1c auction. I've done this a zillion times, and no one has ever snuck in and stolen an auction from me. Just be quick about it. Now use this alt's hearthstone and post the shards, etc on the AH.
At this point u can fly your opposite faction Alt back to the neutral AH and just make another alt and park him in the major city. You now have money on both sides of the AH and can make an absolute killing trading back and forth. I do this on separate accounts so I can 2-box the neutral AH transaction, but you can do it the old-fashioned way too.
Major Money Makers for me include (items with large price differences):For instance, on my server, Large Prismatics sell for about 18g on the horde side and about 30g on the alliance. I've made well over 2k gold in two weeks with pretty much no work involved. Once you get this system started, its easy riding the rest of the way. You can check 3-4 items per day and make hundreds of gold. Never do a daily again.
- Large Prismatic Shards
- Greater Eternal Essences
- Large Brilliant Shards
- Adamantite Ore
- Jewelcrafting Gems
- Primals (not as much as the others tho)
- Lvl 70 BOE Epics and blues
Edit: To pass gold from one character to another, buy alot of an evenly (or favorably) priced item on one side, post it for 1c on the neutral AH, and then sell it on the other side.
If you are using auctioneer to keep track of prices, a really handy command is:
/auctioneer also yourserver-oppositefaction
i.e. /auctioneer also cenarius-horde
It shows the prices for both factions on the same tooltip so you can keep track of things easier.
p.s. I didn't mention this because its already been said by other people, but you can augment this with professions i.e.: Prospecting even cheaper ore, cutting cheap gems, disenchanting cheap blues and greens, selling more valuable tailoring cloth, etc.