Today is World Back Up Day. Backing up data should not be a special event. It should be a routine thing, like brushing one’s teeth.
My backup routine: Time Machine runs every hour, this OS X utility updates a separate external drive with changes to my main drive. A running incremental backup. It keeps several past versions of files. This is really useful for recovering from an accidental deletion of a file or putting back a file back as it was after making a change that was not an improvement.
My next level of backup is a program called SuperDuper!, which makes an exact, bootable copy of my primary hard disk. I make a SuperDuper copy to a raid level 0 mirrored pair external device every other week or so. And on a monthly basis I make a SuperDuper backup to an external drive that I keep in a safe – this drive is connected only when backing up. This is my recovery if my house burns down or my gear is stolen. My safe is fireproof, weighs over 1000 pounds, and it would take industrial machine tools or high explosives to break into it.
One important point: You do not have a backup if you have not tested your backup data by restoring some files and verifying that they are correct.