|If you have a business or not backing up your data is a key principle for success.|
This is part of the preparation principle, yet so important I've created a separate principle on it.
The best way to prepare for a disaster is to ask "What if?" Come up with a number of scenarios so you can see if you're properly mitigating your risk.
You should backup your data or files as often as needed. What would happen if you lose your data? What would be the cost? What if you lose customer's data. If you have a business you need to have this process in writing and someone responsible for carrying it out.
You also what to keep multiple versions of your backed up data as if you only keep one version that one may also have issues. You need to determine what is optimal for your business.
Backups must be stored offsite. If you leave your backups in your office then theft or fire will render them useless. This is not cost-free but the alternative of your entire life's work or business evaporating is pretty scary.
You want this process to be as automatic as possible. There are many companies and software products that can help with this. What if you have paper records like a doctor or lawyer. Consider what will happen if these documents are destroyed. It may pay to have a service that does this for you like Carbonite.
What will happen if you lose it?
There's a fire, flood or theft at your office. What do you do now? How do you get your business back online?
You should also have a location where your passwords are kept as you may lose these and can't get onto your backup computer or server.
You must periodically test your backup processes. If backups are automatic can you restore your data? What's the process for backing it up? Who is running this? What can go wrong? You should check your processes at least 2x per year.
I use a lot of Microsoft Excel and I have a number of processes to make sure my data isn't lost.
I version my excel files starting with .001 to .999. I also have the process automatically save if it hasn't been saved for 20 minutes.