Stolen from the FAQ at a WiiSave.com:
How to Share / Use Wii Game Saves
(Updated 11-2-06 1:16AM)
There are still a few questions that need answering, but here's how we think it works so far: You need to update to the latest firmware. If you're trying to share saves with just the first update, it wont work, you'll get errors. You need to update at least two times (two different updates) in order for everything to be happy (in theory). We're not sure what will happen with future firmware updates.
When transferring saves over the internet, zip them. We've had some issues while transferring the original data.bin files, but we're not positive if this is a real issue yet as we need to confirm which firmware version they originated from. So far, no one has reported a plain data.bin file actually working that has been uploaded to Wii Save.
How do I backup / transfer my saves to an SD card?
From your Wii main menu: Wii Options > Data Management > Save Data > Wii. You'll see all of your Wii saves that are currently on your internal memory. Select the save you want to backup / transfer and select 'Copy' (you need to have an SD card in).
The save is now on your SD card.
How do I upload my save to Wii Save?
Short version: Zip it with the file structure in-tact, register on Wii Save, upload.
Long version: First, put your SD card in your computer (you'll need either an SD card reader built in to your computer or a USB SD card reader). When you have your computer reading the SD card, you'll see a folder named 'private' on your SD card, zip this folder (in winXP) by right clicking on it > send to > Compressed (zip) folder. Note: If you had multiple saves on your SD card, open up that new zip that you created and delete all the games that you don't want included in that zip. If you have more than one in there and don't know which saves are which, just refer to the game list.
You'll then need to register an account. After registering and logging in, you'll have a new option at the top right called 'Upload Save'. Click that, fill out the form, and it should work. Please make sure you test your download after uploading it to the site, sometimes it gets corrupted on upload. If this happens, just delete and re-upload it through your User CP. We're still trying to figure out if that's us or just wonky saves.
How do I use someone else's save?
Backup or delete your original save, if it exists, first. It wont allow you to overwrite anything on your Wii internal memory. After downloading a save, you'll either get a plain old data.bin or a zipped file.
If you have a data.bin, you have to place it in a folder structure on your SD card like so: \private\wii\title\GAME\data.bin (replacing GAME with it's corresponding game code from the game list).
If you get a zipped file, it most likely has all of it's folder structure in tact, so all you have to do is extract it to your SD card so it shows up like the above folder structure.
Once you have the file in place on your SD card, you can then put the SD card in to your Wii and go to your saved game(s) on your SD card (Wii Options > Data Management > Save Data > Wii > SD card tab), select the saved game that you want and select Copy. Keep in mind that if you have a save from the game you're trying to replace, it wont overwrite it, so you'll have to backup your save, then delete it off your Wii internal memory to be able to transfer the new one on.
I'm looking at my /private/wii/title/ folder and I don't know which game is which!
Just refer to this Game List:
Legend of Zelda: Twilight Princess - RZDE
Wii Sports - RSPE
Rayman: Raving Rabbids - RRBE
Trauma Center: Second Opinion - RKDE
Red Steel - REDE
We'll have a better game code list system up soon.
I did all that and it doesn't work!
Check and make sure your 4 letter game code is correct in your folder structure. If everything still looks correct, then it might just be a bad save.
Try posting a comment about it for more help.
lets get goin! anyone got all the goodies unlocked in Marvel yet?