Read Thread: Am I Drunk?
I use Ubuntu Linux so I use Déjà Dup Backup Tool. I have it set to do incremental backups (backs up changes) every day. It also does a full backup every two weeks.
Since most of you use MS Windows, I looked up Five Best Windows Backup Tools. Kim Komando also has some good recommendations, like this one.
And here are some programs for Macintosh users.