Floppy disks are not really a suitable media for making backups as:
The media is unreliable, especially over long periods of time
Backing up and restoring is very slow
They have a very limited capacity (the days of backing up an entire hard disk onto a dozen or so floppies has long since passed).
However, if you have no other method of backing up your data then floppy disks are better than no backup at all.
If you do have to use floppy disks then ensure that you use good quality ones. Floppies that have been lying around the office for a couple of years are a bad choice. Ideally use new ones from a reputable manufacturer.
The best way to backup to floppy disk is to use tar(1) with the -M (multi volume) option, which allows backups to span multiple floppies.
To backup all the files in the current directory and sub-directory use this (as root):
# tar Mcvf /dev/rfd0 *
When the first floppy is full tar(1) will prompt you to insert the next volume (because tar(1) is media independent it refers to volumes. In this context it means floppy disk)
Prepare volume #2 for /dev/rfd0 and hit return:
This is repeated (with the volume number incrementing) until all the specified files have been archived.
Unfortunately, tar(1) will not allow the -z option to be used for multi-volume archives. You could, of course, gzip(1) all the files, tar(1) them to the floppies, then gunzip(1) the files again!
To restore the entire archive use:
# tar Mxvf /dev/rfd0
To restore only specific files you can either start with the first floppy and use:
# tar Mxvf /dev/rfd0 filename
tar(1) will prompt you to insert subsequent floppies until it finds the required file.
Alternatively, if you know which floppy the file is on then you can simply insert that floppy and use the same command as above. Note that if the first file on the floppy is a continuation from the previous one then tar(1) will warn you that it cannot restore it, even if you have not asked it to!