This is the official working Dupe for 1.11b. I tested it out myself and it works great. This is the one that those stupid sites are selling and how all those guys are getting 100s of Sojs to sell on Ebay.
There have been variations of this dupe released, but certain details have always been left out which are key to its success. We will provide all of them.
Requirements
1) A necromancer with bonewall (preferably high level) and at least 125 percent faster cast rate.
2) A sorceress with meteor. Her cast rate does not matter.
3) About 10-20 minutes of your time.
The Dupe Process
1) Make a game that has a bridge leaving town in act 1, and step a bit out of town.
2) Stand outside of town but still slightly within the view of the bridge, so that you have a full map to work with and spam.
3) Spam with the necromancer using bonewall until you cover the entire map, and then spam to fill all holes with the sorceress with meteor and then try to cover the whole map with meteor. The map will now start to turn invisible.
4) Your body will start to become covered by the invisible map. When this happens create a game on your second D2 Window with the same character. If you get a FTJ game error, try to spam more in the other game and keep trying to create the game.
5) Join a mule game and drop some items, it doesn't matter what really.
6) Now, back in the laggy game, you need to very slowly walk to act 5, and then quickly move back to act 1 and drop everything that you want to dupe. Leave the game without temp-perming and bring your mule. (The walking helps prevent you from dropping out of the game)
7) Pick up the items and temp-perm the mule (go into a trade screen with someone)
8) Temp perm your necromancer in the 2nd game.
You now have a mule with temp-permed items and your originally necromancer with temp-permed items.
Officially: That is how you dupe.
Your welcome.
And remember, Together we CAN make blizzard reset the ladder!