It’s worth refreshing all your Finder Aliases before copying or cloning a volume to update their link info. Here’s a free tool to do that and more: Alifix.
I’m sure this used to be much easier in HFS+, but here’s a detailed set of instructions for making a bootable clone in High Sierra or Mojave, for an APFS disk.
Don’t just throw it in a box and send it off: what happens if its internal storage is replaced or wiped? What about protecting sensitive files? Does a T2 chip make this difficult?
What if you can’t or don’t want to use Migration Assistant to move your files from your old to a new Mac? Here it can get more complicated. Tips and solutions to help.
Do you know when it would be best to use a hard link? What’s the difference between a Finder alias and a symbolic link? And where to High Sierra’s new clones fit in?
Does APFS support its major new features – clones, snapshots, etc – yet, and how can you use them?
How often, and how much? Decide by thinking through how you would use your backup to restore your Mac after disaster.