First and foremost, I apologize to those who are against duping. Everyone is entitled to play the game whichever way choose. To those who are afraid of duping corrupting their game: I have never heard of someone’s game corrupting from duping. If it did, the game would have been made poorly because it is the equivalent of your wifi cutting out during the save.
For those of you who don’t know what duping is, it is the duplication of in game items. This means that you can copy any item in the game that may be dropped outside. Whether you are duping for yourself or duping to help another, always make sure that it’s with someone you can trust. Stealing while duping items with someone you’ve just met is fairly common in the community. A helpful tip is to add whoever you’re duping with onto your best friends list so you can communicate via the game itself. It’s easier to let the host know if their town had been shut because of the switch being flicked incorrectly and helps both sides work out the details.
If you are visiting
Make sure you have added the host and that their gates are open. You will be the one visiting their town and doing the actual flicking of the switch. If you don’t already have the items that you’ll need to be duping, the host should have them laid out on the floor right next to the train station. Pick everything up (side note: you may use letter and locker space to hold extra items) and signal the host to let them know that it’s time to save. Drop all of the items back onto the ground again. If you already have the items that both of you are duping, you may skip the previous segment and just drop the items onto the ground seeing as the game already saved once you entered their town. At this point you have two options: leave via the train station or asking the host to end the session. If you’re going to continue duping items, leave via the train station. Make sure not to flick the wifi switch off while you are boarding the train. The saving screen comes up as soon as you’ve boarded and the screen is black with the save circle at the bottom right. If both of you are done after this, ask the host to end the multiplayer session.
Many people debate on when to turn your wifi off by flicking the wifi switch on the side of your DS, but to properly explain I’ll be comparing the save screen to a clock. The ideal time for you to flick the switch is during the second spin around where the 9 is on a clock (or here if you’re a visual person). I usually begin flicking the switch around 11 (here) on the first spin to guarantee that it’ll land on 9 the second spin but that is because I flick slower. Keep note that the saving screen speed will vary on both of your wifi connections so when to flick may vary for you. Try on useless junk prior to duping valuable items just to make sure that you have the basic idea of what you’re doing. Regardless, it must land on 9. If you flicked too early the possessions will still be in the person’s town and their gates will more than likely have closed off. If you flicked too late the items will remain with you but not in the host’s town.
If you are hosting
To begin, set the items that you need duped right beside the entrance of the train station and open your gates. If the visitor has the items you both will be duping, don’t worry about leaving the items besides the station but you should still kick off your paths or make room for the visitor to drop items. Making someone run halfway across your town wastes their time and is a huge hassle. My biggest tip of advice is to pay attention while the visitor is duping. Hosting is the easier role, and it’s always a pain as the visitor when you have a host that doesn’t maintain a level of communication during the duping process. If the visitor is picking up the items that need to be duped in your town, save as soon as everything is in their inventory. The visitor will then drop everything onto the floor. If the visitor is going to dupe more, they should leave via the train station. If they are only duping a select set of items, they should ask you to end the multiplayer session which can be accomplished by pressing start and then “End Multiplayer Session.” Always make sure with the visitor that your gates are open, and double check after completing that the items are still in your town. This will make things easier for both of you knowing if your attempt was a success.