Online backup

The critical thing with backup is low or no maintenance. You may think you will remember to back up every week, but the laws of human nature predict that as backup is not normally "front of mind", and so you will forget.

I use all of the following:

1. RAID 0 (mirror) for my data disks.
2. Sync with external HDD.
3. Carbonite (offline backup). The other benefit is that you can access your files through a web browser if you need to.

Most users should use online backup such as Carbonite.