Backing up a Wordpress instance manually is, obviously, a good idea, but I have pretty much stopped doing it myself. Why? Because doing it manually means having to login via FTP and (slowly) download all your files, then login to the MySQL server and export a copy of the tables - too many steps, too many moving parts, and the end result is too clunky to be quickly and easily used if the site goes down.
Instead, I have been using a free Wordpress plugin called “Duplicator” - https://wordpress.org/plugins/duplicator/. It automatically dumps the DB to an SQL file, along with all of the files within the Wordpress instance (although you can set filters to exclude any files you want to ignore), and creates a ZIP file of the lot. It also creates a PHP file which, when uploaded to a server alongside the ZIP file allows you to quickly and (insanely) easily reinstall the snapshot. It is also a dream for server moves or domain changes.
So much easier, so much more powerful, simple enough that I send my clients the two files (PHP and ZIP) when I finish a build for them and they can then install it onto their production server with very little effort on their part. I also use Duplicator to take snapshots of my sites at regular intervals and then store those files on Amazon S3 as a complete rolling history of the entire site (should I ever need to recover it).