Minecraft TooManyItems?

I have a mac and I want to install it, so I went to application support, made minecraft.jar a folder dragged the classes but not the readme into the folder, named the folder minecraft.jar, deleted the META-INF folder. It let me log in but then black screened. I tried 6-8 times and it would do the exact same thing each time. What am I doing wrong? Please help!