Your Mac ships with amazing backup software called Time Machine. It requires an external USB drive which you can buy at the Apple Store and they’ll probably show you how to get Time Machine setup.
You can also get slightly cheaper options on Amazon but without the help from the Apple Store.
To setup Time Machine yourself, follow this Youtube video
Using Time Machine for backups is easy and convenient, but its not bullet proof. The USB drive might fail over time or you get out of the habit of connecting your USB drive to your Mac (don’t!).
To give yourself extra confidence and reliability use a cloud backup service. An online backup service provider will install backup software on your Mac and copy files to their servers where your data is held securely and safely.
Copying files over your home broadband connection can be slow and the first time you set up an online backup provider it may take several days for the service to copy all your files. Just leave your Mac switched on overnight and let the software do its business.
For value and ease-of-use I recommend using Backblaze. $5/month is money well spent.
If you’re of a geek-persuasion and are comfortable using Amazon S3, I recommend using ARQ. Using ARQ and S3 Glacier works out slightly cheaper over time but involves more technical effort getting it set up. Its the option I use personally.
Image provided by John Kay.