When it comes to making gold, and playing the auction house, there really is one sure fire means of generating an income on most servers: cross faction trading.
I’ve refrained from touching on the subject before, because you’ll find quite often this is a “no-brainer” type of activity that people constantly flog when discussing gold making. I guess that makes me a lemming, but with Cataclysm approaching it’s really important to reiterate if you want to see your profits pour in (and really, who doesn’t?). However, this trick requires one tiny little detail to pull off: a second account.
If you’re lucky and you have someone else in your household who plays, this isn’t a problem. You just get them to park one of their toons at a neutral auction house (Gadgetzan or Booty Bay), and one of yours as well. Just be smart enough not to make them the same faction. Of course, if you can afford two accounts, you’re even more ahead of the game. If neither option presents itself, well then you need a friend to go with you and entrust in them to not run away like a thief in the night with your gold or possibly goods. You’ll use one toon to sell to the other and then have the items mailed to your banker to sell. Just remember, if the second account involved in this ordeal isn’t your own, be sure to tip the person involved. I tend to use someone’s toon and each time I send 5k over to the opposing faction through this person, I let them keep 100g.
The best way to make buying from one side and selling to the other is immediately figure out what side has a higher population. This is the side where the good stuff has a better chance of coming in, and subsequently will allow you to sell to the short-supplied faction at a lovely profit. In my case, Horde side outnumbers Alliance at least 8-1. So much of the endgame crafting ingredients have been coming over (Saronite at 9g a stack!!!!) and making a tidy sum the other way.
Remember not to limit yourself to this strategy, though. There are some bind on equip or usage items that are limited to one faction or the other and selling it the other way can have benefits as well. The most obvious one is non-combat pets (especially the Argent Tournament ones), which on the opposing faction can net you several gold each in profit, and be moved quickly.
With Cataclysm coming, the race will once again be on to reach end game and farming and crafting. Inevitably you’re on a server where one faction is going to do this at a much better rate. Some are balanced, but most aren’t. Set yourself up now, park your toons, and start counting even more stacks of gold!