1. Register a free account at http://www.minecraft.net/
2. Login at http://mineshafter.appspot.com/ With your gmail account.
3.Go to minecraftskins.com, pick your skin and downlaod it.
4.Go back to http://mineshafter.appspot.com/ and Upload your skin in the Settings bar (under your logged in account name)
5. Connect your minecraft.net Account in the Settings bar (under your logged in account name) (in the mineshafter.appspot.com)
6. Download http://fileml.com/02Gx61 And put it in your Minecraft Folder.
7. Run the mineshafter-proxy.jar (downloaded file) from your game folder. NOTE!!!: Always run your minecraft from the mineshafter-proxy.jar so the skin changer can work!
8. Log in with your Minecraft.net account