By far the easiest way to install Debian GNU/Linux is from an Official Debian CD-ROM Set. You can buy a set from a vendor (see the CD vendors page). You may also download the CD-ROM images from a Debian mirror and make your own set, if you have a fast network connection and a CD burner (see the Debian CD page for detailed instructions). If you have a Debian CD set and CDs are bootable on your machine, you can skip right to Chapter 5, Booting the Installation System; much effort has been expended to ensure the files most people need are there on the CD. Although a full set of binary packages requires several CDs, it is unlikely you will need packages on the third CD and above. You may also consider using the DVD version, which saves a lot of space on your shelf and you avoid the CD shuffling marathon.
If your machine doesn't support CD booting, but you do have a CD set, you can use an alternative strategy such as hard disk, usb stick, net boot, or manually loading the kernel from the CD to initially boot the system installer. The files you need for booting by another means are also on the CD; the Debian network archive and CD folder organization are identical. So when archive file paths are given below for particular files you need for booting, look for those files in the same directories and subdirectories on your CD.
Once the installer is booted, it will be able to obtain all the other files it needs from the CD.
If you don't have a CD set, then you will need to download the installer system files and place them on the hard disk or usb stick or a connected computer so they can be used to boot the installer.