Your personal files and settings are usually in your home directory.
If you have the room, it is best to backup the entire home directory with the following exceptions:
Files that you have copied from a CD, DVD, or other removable media, since it would be faster to copy them again than to restore them from backup.
Files that you can generate easily. For example, PDF's that can be generated from TeX files, or object files that can be made with make. Just make sure the source is backed up.
Your trashed files, which can be found in
The amount of data you can backup is limited by the size of the storage device.
One simple way to backup your files is to just copy them to a safe location, such as an external hard drive, another computer on the network or a USB drive.
One such app is
The