It is only when you realise some data has gone missing that you really appreciate the importance of this question.
The topic actually divides into three sub-topics:
- How do I get back a file I just deleted or overwrote by accident?
- My disk just failed; how do I get my data back?
- My disk is full; how do I create more space?
The first is really about snapshots. You need to consider how frequently you need the snapshots and how long it might take you to realise you need the snapshot.
The second is about backup/recovery. You need to consider how far back you would be prepared to fallback (one day, one week?) and what data is actually really critical to you.
The last is about archive/restore. You need to consider realistically how far back you want to look in historical documents. It would always be possible to restore them if you need them, but do you really need instant access? Do you really need to keep backing them up?
The answers to these questions vary. If your entire business is run from one laptop or PC, then there is one set of answers. On the other hand, where more than one person is involved, the answers are more complex. In both cases, the current trend is to backup offsite by using a cloud-based service over the Internet.
The best idea, even for a single user, would be to use a cloud-based service to share data anyway to avoid difficulties related to the disk on laptop or PC. However, this does introduce more complexities when you answer the questions about the Internet connect and the Router the business requires.