The 3-2-1 rule: 3 copies, 2 different media, 1 offsite
Keep three copies of anything that matters: the original, a local backup (like an external drive), and one copy somewhere else (the cloud counts). It sounds like overkill until the day your house loses both the laptop and the drive sitting next to it.
External drive + cloud backup is the minimum
For most homes, one external hard drive that backs up automatically plus a cloud sync service covers the 3-2-1 rule without any effort after setup day. The key word is automatically — a backup that depends on you remembering isn't a backup.
Google Drive, OneDrive, and iCloud all work — pick one and actually use it
There's no meaningful wrong choice among the big three. What matters is that it's turned on, it's syncing the folders you actually use, and you haven't quietly run out of storage space — which is the most common silent failure I see.
Back up your photos first
In years of doing data recovery, photos are the thing people grieve. Documents can be recreated; the photos of your kids can't. Whatever backup you set up, confirm the photo library is in it before anything else.
Test your backup occasionally
A backup you can't restore isn't really a backup. Once or twice a year, pick a random file and actually restore it. Five minutes of checking beats finding out the backup was broken on the day you need it.
I set up automatic backups that don't depend on anyone remembering — and if you've already lost files, data recovery is one of the things I do most.