First rule of backups - backup frequently.
Second rule of Backups (the one everyone forgets) - TEST YOU BACKUPS.
Third rule of backups - back up to multiple locations/devices.
I use SyncBack Free to run off copies of everything to the servers, at work - yes, they allow it, we're small and have a lot of spare capacity, and I'm the IT guy.
At home I copy everything to a Buffalo NAS that has 4 drives in a RAID5 configuration. Plus there are a couple of USB drives around with backups on them.
A couple of a350's, an a700 and now an a580, plus even more lenses.