There is two ways you can do this that i know about.
>>>In order to enter BT you must be attuned<<<
If you don't know if you are attuned or not just think did you ever down the last boss in TK and SSC?
1. Shadow priest soloing trash mobs in the BT. You dot and just run for a good 5 min.
Video on it [ame=http://www.youtube.com/watch?v=lYns6mfWH0M]YouTube - Shadow priest farms Black temple[/ame]
2. Warlock to help give a SS. A healer class that can rez and a dps class that can solo the mobs. . IMO you make more money doing this. This you need patience. What you need for this is 2 people minium you can't solo. 2 invisibility pots. What you do is run up run to a safe spot and you wait 10 min on you invisibility pots to come back you run up the stairs and you solo the trash mobs. You get epic rings most of the time. You get nice loot and if i don't want D/e and thats good money you also get VERY NICE GEMS in there. Here is the video on what 1 healer 1 dps did.
Video on it [ame=http://www.youtube.com/watch?v=Bu8E39eezEQ&feature=related]YouTube - earn up to 3000 gold in 20 minutes[/ame]
I'm very sorry if this a repost just wanted to share this out! GOOD LUCK everyone.
There are many other ways to do it but, these are my way on doing this