I'm a pro at this, I currently have 2 scammed accounts and my own account which I done myself.
First of all:
Find a person YOU KNOW that isnt the origional owner of the account (Login)
Agree to trade them (whatever level 70 you have, or characters they have agreed to trade with/ If you dont have any, there is a guide on how to fake them)
Have a "middle-man" one of your trusted friends, have them logon your account and enter the "change password" in the account interface, have them put in a new password etc.
Ask them to change the email of the account to your email, ask them to send a screenshot, and you will change the email on yours to theirs, and send a screenshot.
Make sure they send first, from there you can just edit their email into the screenshot you have taken.
Exchange the info.
Alternate way:
Have them exchange the info, and then you do the same.
When you have their info, buy yourself 20 seconds and logon to their account, change the password and then hand over your own, at the same time as handing over your own account details, ask your "middle-man" to accept the password change, thus you gaining an account, and keeping your own.
Note: This doesnt work 100% But it worked for me every try.