When you are working in the Studio you should save your work in a folder with your name, in one of the 'Scratch' drives. You can make a new folder by holding down the 'control' key while clicking where you want the new folder to be, and selecting 'New Folder' from the menu that appears. The 'Scratch' drives are 'local' drives (meaning that they are stored on the hard drive of the computer you are at, rather than on the network), so you'll need to either transfer your work via the Media Server or burn a CD/DVD if you want to work on the same project at another computer. The 'Scratch' drives are the only place on the Studio Mac that you should save work. 

You should always make backups of your work (by burning a CD/DVD of it, for example). As everyone can use the 'Scratch' drives, you can't guarantee your work will be there still next time you use that computer.