Don't just do backups. Think through failure modes. Here are some examples to think through:

BAD: I accidentally deleted a directory and lost several months of work. RAID immediately mirrored the delete! Shit I thought RAID would protect me.

GOOD: use zfs or btrfs and take snapshots.

BAD: I've been backing up to a NAS but then I got cryptolockered, and they got into the NAS and cryptolockered that too!

GOOD: disconnect your backup system from the network when it is not running backups.

BAD: I've been making offline backups, but also defying the government. They came and raided the house and took my computers AND the backups.

GOOD: take backups offsite.

BAD: I took my backups offsite to a friends house, but we got into a fight. Now I have no backups.

GOOD: I treat my friends very well.

BAD: I took my backups offsite to a friends house, but it turned out he was an FBI agent.

GOOD: I shake down all my friends, and put them through torture sessions to extract all useful information before I trust them.