What information do you need to backup? Your home directory, presumably, but something else? The apps you don't have to backup since you can get them from the net, and I'd think most of your configurations and stuff reside under /home/$USER
If you mean by what means you do the backup, the simplest way is just to create a file archive and possibly compress it a bit. For archiving I'd use tar (if you only have normal files) or cpio (that's an easy one). After archiving, use some other program to compress the file so it becomes smaller and so easier to move around; I'd use either bzip2 or gzip (bzip2 is a bit slower, but produces smaller package).
Since your personal configurations mostly reside under your home directory, you could create a backup using cpio and bzip2 (provided you have those installed) by
Code:
find /home/$USER -print -depth | cpio -oc > /tmp/backup.cpio
bzip2 /tmp/backup.cpio
After this you'd have your home directory compressed into a /tmp/backup.cpio.bz2 file, which you'd then move to another place or perhaps burn on a DVD or some other media. After the installation of the new system, you'd copy the file to your home dir and use
Code:
bunzip2 backup.cpio.bz2
cat backup.cpio | cpio -iv
to extract the contents. If you extract the contents using absolute path names (like above), you better have the same username on the new system (or at least the same name homedirectory). If you use relative pathnames instead (--no-absolute-pathnames), you get a directory under your homedir which you can then use to copy the data off.
That's only one rude example. You've got multiple ways of doing that.
EDIT: and that, of course, is because in Unix and alike systems nearly everything, if not everything, is understood as files (files, directories, devices...) so all the configs usually reside in some sort of file too, and user data is almost always under the user's home dir. Unlike in Windows.
