The process to backup your data can be as basic or as complex as your business requires it. This guide is meant for small local businesses, and we'll try and keep it simple and not too costly.
First you need to figure out "what" it is that you should backup. The important files might differ from place to place, but you probably know which ones they are, like an important Excel spreadsheet, or an Access database; maybe your accounting program cam create a backup file for you every week.
Maybe it's not just a document or two, maybe your whole computer has been setup for a very specific tasks, like a cash register, or for running some other machines, and you need to be able to rebuild it exactly as it is configured right now.
So now you know what needs to be backed up. The next question for you is, do you want to make a copy to something physical like a USB Flash drive, or an external hard drive? Or are you comfortable with copying your information to a cloud service? This of course will depend not only on your taste, how much storage you need (the cloud option gets expensive fast), and if any regulations apply to you (you might need an option with encryption, but that is beyond the scope of this article).
The lowest cost option, and most familiar, is to get a couple of USB flash drives and copy your documents regularly to them. You should keep one in a secure place on premises, and the other one at an alternate location (in case of fire or theft). Please buy a brand name one, like Kingston, Sandisk, Verbatim, Patriot, as other cheaper options might not be as reliable. In any case, please note neither brand will last forever, and you should get a fresh USB flash drive every year.
If you have a large amount of files, or you need to backup your whole computer system, look for a good external hard drive, preferably one that already comes with backup software that you can install and have it take care of this task for you (other than you being required to plug the external hard drive in regularly to let it copy the data). An example of this type of device is the Western Digital "My Passport", or the Seagate "Backup" line. You should get a new one every 3 years to be on the safe side. If your disk did not come with a program to backup your computer, there are good free options, like EaseUS Todo Backup Free, Macrium Reflect Free, or for $40 USD, Paragon Backup.
Now if you want to backup to the cloud, there are lots of options out there, and levels of price and complexity. The most basic one you can use is OneDrive from Microsoft (the first 5GB are free), and it's already on your computer if you have Windows 10.
If you want to backup your whole computer to the cloud, then the most popular option is Carbonite, which starts at $60 USD for one computer. Keep in mind that aside from the cost of this service, if your internet provider is enforcing a monthly data cap, your internet bill might go up considerably.