If you are on a network, perhaps you can copy your data to the file server. Your system administrator will have to provide a place for your data and a time for you to do the backup. If you are not connected to a network, or if you have a large quantity of data on a networked PC, a tape drive is essential. Tape drive prices have dropped a lot. Back up the entire hard disk once a week.
Most people can use floppy disks for daily backup of files which have changed.
A typical computer user can do daily backups to the same floppy disk for an entire week. Each backup will only copy changed files, so it should be fast. If you change a file repeatedly, the floppy disk will have the latest version. However, database files are sometimes too large for one floppy disk. Then backup to a file server or tape is preferable.