Use the copy save file feature in Save Data options. Unless the game is copy protected it should transfer right over. Otherwise make sure both consoles are softmodded and use SaveGame Manager to extract the save and import it to your friend's console.
And because you didn't post in the intro section here is some additional info for you.
Hello Kratos200 and welcome to Wiihacks.com, the world’s largest Wii modding and forum community.
We have the most comprehensive collection of useful Wii-related guides, tutorials, and articles on the net. You can find links to our most popular guides at the Wiihacks Ultimate Index. Another incredibly useful guide for new members is HERE.
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Many of our newest members have questions which can be answered in the Tutorials Section. To get started with softmodding, please find the firmware for your console (Wii Options->Settings->Top Right-Hand Corner) and head to one of the following guides: Any 3.1-4.1 Wii, Any 4.2 Wii, or Full Hacking Guide for 4.2 Wiis.
If you run into an error, please refer to the Error Index.
There are two methods for running your backups: Disc or USB. If you purchased your console after late Summer-ish '09, you could have a D3-2 drive which prevents backup discs of any kind from playing.
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