Now in patch 3.2 you can make both alliance and horde on same server.
So from the start you might need some gold?
Make a new char with a friend on the other faction lets say alliance. now make a run to bootbay, go to the ah and put out a random item for a good amount of money like 2k. now you have to logon to your main char on the horde side and just go to the ah and buy your friends item and your friend buy yours.
when you alliance has that gold you can post items from your main thats boe, think you can have a little lower price then that because i dont think theres so many using that kind of ah, but its up to you.
tip for cheep people make sure you take 12h ah post to save deposite money.
So now you ally will get the gold you can do the same thing with boe items.
I have not tested if you can buy your own item on the ah maybe someone can test it out
well this is some basic fact but if you didnt know now you do
dono if this has been a repost or not, na well enjoy