Using a program called NetPeeker, available from (
http://www.net-peeker.com/Download.htm) (or some other lag inhibiting program) you can cause intentional lag, making it easier to dupe items and so on, two characters are recommended for the duping process but is not required, you can do it with a friend as well. For this to work you need to do the following:
1. Set the maximum down and up speed to about as low as you can go without losing a connection (Probably around 24k)
2. Log on etc. and then locate an NPC to which you can send items.
3. Place the desired items in the box and hit send (you can send them to yourself if desired)
4. Return to the mog house of the character to whom you sent the item/gil to and open up the delivery box.
5. (help by another person is good on this part) right as you hit an item to take out of the box, pull your network cable out of the wall, or computer for about 5 seconds, then alt-tab your game and replace the network cable, and log back in. The items should have been duplicated ^^ have fun with that one.
If i can do it, I'm sure you can manage =)
Removing your sub-job
Another way to use this program to your advantage is by using it to make lag again (same settings as for the duping), and then do the following:
1. enter your mog house
2. open up the job selection etc. (you have to do the next part fast!!)
3. Change your main job to any job, it doesn't matter
4. Now as quickly as possible set your sub job to what your main job was before you changed it, and then select your main job as the same as before (if you do it quick enough you should be able to select it irregardless of what you set the subjob to)
5. If this doesn't work then, use the "pull the plug technique", right as you go to set your main job back, remove the network cable and after you've selected it, return it to the jack in your computer and/or wall.
Well I hope this helps those in need, premium would be nice for this ^^
P.S. if you use windower in conjunction with this it helps (Job Exp)