I grew up in Des Moines, Iowa, so when I moved to Southern California about 15 years ago one of the first things I did was get certified in Scuba Diving.
Scuba Diving has a rule called the Buddy System, a pretty simple rule saying that you never dive alone. This is a basic backup strategy, as long as you have a buddy you have a backup air supply in case yours runs out early or someone to help you if something goes wrong.
I have this conversation a lot and the question I always get asked is:
"What do I really need to do for backup?"
You can get really crazy with this stuff but when you get too crazy, it's not good, you end up wasting your time.
The real minimum for data is having everything on a RAID and at least one backup of all of your data and then you're safe. You can backup in a bunch of ways:
There's a lot of other things to consider after that but consider this your baseline buddy system.
Just like in scuba diving you want to be with your buddy but that's not all you should be thinking about. But if there's one big rule to be thinking about RAID protection and at least one backup.