After Nintendo revealed that users would be able to transfer their Wii user data to shiny new Wii Us, several outlets turned to the console’s manual to find out precisely how.
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The process seems a little cumbersome. You’ll first need to insert an SD card with at least 512 MB of RAM into your Wii U, and ready it using a transfer application.
After that, the SD card has to be swapped into the Wii, and you’ll have to download a data transfer application and follow the instructions.
The last step is returning the SD card to the Wii U and finalising the procedure.
Both consoles will have to be connected to the Internet, and you’ll need a controller for each one. Once you’ve transferred the data, there’s no going back – so be very sure.
You’ll find more detailed instructions on several sites which have posted unboxing features – try Joystiq, IGN, Polygon, GameInformer or Destructoid. But remember – there’s no substitute for RTFM.
~ Source