How do I make a physical backup of Of OS X Lion?
The first step will be to download mountain lion from Mac application store as usual. Once you get it, open a finder window and locate the OS X installation file, which you have just downloaded. After that, right click on it and select 'show package contents'. Read more on http://www.mactrast.com/2012/07/how-to-create-a-physical-backup-of-the-os-x-mountain-lion-installer/.
Get an external hard drive, and then it should ask if you want to set up time machine. Say yes.