Quoted from Risugami himself.
1) Open up %appdata%, if you don't know how to do this, start>run, then type in %appdata%
2) Browse to .minecraft/bin
3) Open up minecraft.jar with WinRAR or 7zip.
4) Drag and drop the necessary files into the jar.
5) Delete the META-INF folder in the jar.
6) Run Minecraft, enjoy!
1) Go to Applications>Utilities and open terminal.
2) Type in the following, line by line:
jar xf ~/Library/Application\ Support/minecraft/bin/minecraft.jar3) Outside of terminal, copy the class files into the mctmp directory.
4) Back inside terminal, type in the following:
jar uf ~/Library/Application\ Support/minecraft/bin/minecraft.jar ./
rm -rf mctmp5) Run Minecraft, enjoy!