For primary backup, I use external USB drives.
About every 3 months, I take a full backup of my computer then take it to the safety deposit box. backup A.
3 months later, I take another full backup of my computer then take it to the safety deposit box. backup B
3 months later, I take another full backup of my computer then take it to the safety deposit box. backup C
3 months later, I take another full backup of my computer then take it to the safety deposit box. backup D
Then I use backup A to take the next backup.
. . .
So I rotate through 4 or 5 drives.
If there is a problem I have 4 generations of backup that I can go back to.
If I do anything major, I will take a backup after that.
Things like completing my tax returns, processing my nephew's wedding pix, etc.
I take FULL backups to the USB hard drive, because I do not want the hassle of recovering with incremental backups. That hard drive has everything.
The old rule was, if you make enough changes that you do not want to do it over, take a backup.
And if it is REALLY IMPORTANT, take TWO backups, and store the backups in different physical locations.
I use external USB hard drives, because I can copy files to it faster than uploading through the internet.
I also use a cloud backup, which takes a daily incremental backup, and covers me between my USB drive backups.
But that initial cloud backup took several days to upload all the files, which I knew it would take. So I do not do a FULL backup to the cloud, only selected important files. Even so, I have had the daily incremental backup not complete running, after 6 hours. This is because my upload speed is limited by the ISP.
I also do not believe in trusting to only ONE method. Yeah, belt and suspenders.