First of all, this is a tip, not a guide. It is partially a guide though.
Most of you may say it is common sense, but most of you may have not thought of it. It IS common sense though.
This is also server dependant. Well, here goes:
As you know, we can now make both horde and alliance characters on the same server in 3.2.0.
What comes to your mind? You won't want to create a character on the other faction because you can't send him money, heirloom items etc.
But there is another reason why you should make one. You can get money.
You know that the Faction Change is coming too, right?
As you also know, the Alliance and Horde auction houses aren't connected. Which means that the prices differ.
Now it is pretty simple:
You must find an item in your faction's AH which costs less/ a lot less (server dependant) than it costs in the other faction's AH.
So what you need to do is:
1. Make a character from the other faction.
2. You should choose the race whose land is closest to Winterspring.
A) Kill some mobs and get 1 silver or so.
3. Do the long travel and go to Everlook in Winterspring.
4. Now log in with your main and start farming and buying out the item which you are going to sell to the other faction.
5. Go to Everlook with your main after you have enough of the particular item.
6. Put everything for one copper buyout price.
7. Quickly log to your character from the other faction and buyout everything.
8. Now make a new character from the opposing faction. Make it a race whose capital city you can get to faster.
9. Mail all of the items to this character.
10. Sell them all.
11. Do this a lot of times until you get your desired amount of gold.
A) When the price of the item you chose drops on the other faction, you can choose another item. From both factions' AHs actually. There is always one item which costs more in the other faction, so you can use both factions if you have characters of them both.
12. Make a Faction Change to the character from the opposite faction that has the money and then send the money to your main.
A) If you do this enough, you will get a lot of gold.
And that is it.
Q: But why Everlook? I mean, it's a lot faster let's say if I am horde and make a human, I can go to STV pretty fast, there's a neutral AH there too. Or if I'm an orc or tauren, I can go to Ratchet and get the boat to STV, where the Neutral AH is. Why do I need to take the long road?
A: Simple, actually. There are a lot more people in STV and the other neutral AHs then there are in Everlook, mainly because there are more lvl 30-40 in STV while Winterspring is for lvl 55-60, and a lot less people will be there. And most people level at The Blasted Lands/ The Burning Steppes actually.
If you don't care that much for the success of this, then you can put them up in Booty Bay. But there's a big chance someone will have already bought them before you relog. The lowest chance of this happening is in Everlook.
DISCLAIMER: I haven't played WoW since 3.0.9. I'm not entirely sure of some changes that might make this unavailable.
It's also 2:09 AM so I might have made a huge mistake somewhere.
This will only work if you make a faction change (when it comes).