Aight so I dont completely know all the details on this but i heard bits and pieces so trial and error should fill everything in.
1. get something to dupe
2. go to ah
3. put the desired item to be duped in ah
4. take it out and make yourself lag and dc(the part that i cant manage to do)
5. log back on and you should have the item in your inven as well as the AH.
I haven't been successful with it yet but i know others who have. Like i said earlier there may be more steps or different ones that dont match to mine very well but these should be the general idea of it. Also beware if you think GM's are watching you do not attempt. The DC will send flags as any DC does and they will check if you are being watched. If you are just a no one on there that GM's aren't aware of you should be fine.
Sorry if it doesn't work for you, I'm still trying to beef it up myself.