Ok, since i can't search, i havn't been able to check if this is already said.but i haven't seen it so i'm going to give a run of it anyway...
1) go to a wow account selling forum like markeedragon.com and search under the "selling accounts."
2) Find an account you like and add the person selling it.
3) Spend a while asking questions about the account and making yourself sound genuine.
4) When they ask for a price, keep argueing with them about the price so they think you're an actualy buyer, and after a few minutes, agree on a normal price (don't just pay $2000 for a lvl 40 account or it will be obvious xP)
5) When they ask "how you wana do this", you say something like "Change the email to mine first, and then give me your username and password so i can log onto account management and check. Once i've checked taht you're honest, i'll send the money and once you recieve the money, Give me the Sq/Sa"
6) If they don't agree to this, then go find a different person. if they do, then they're noobs.
7) When they change the email, try to find out their full name. Ask things like "can i please have the full name the account is under? Becuase if blizzard questions me, i need all the details!" and most of the time, thye will believe you!
when you have their name, Go search their name or email address on myspace/facebook beacuse most people have that. If you're desperate then search their email address on google.
9) See what their SQ is and try to find their answer on their website.
10) If you Figure it out, CONGRATZ! you have a new account with enough info so that if blizzard contacts you, you will probably seem legit. If you DONT figure it out, change the pass and hope for the best, if they dont cantact blizzard, then they can't reset heir account because its under your email! so CONGRATZ! you have a 25-50% chance of have gotten the account.
TIPS:
This works better if they other person is not OO so they might not be able to contact blizzard and recover it beacuse they don't have CD key...