The only real and best thing to do are backups. Lots of backups. Also offsite (physically or in the cloud) backups.
It's not just the hard drive that can fail. Think stolen machine. Or a fire or flood in your home. Or your cat walking across your keyboard at just the wrong time. Or you deleting something important by accident. Or malware that takes over your computer and wants payment before you see your files again. Or just the gods deciding that it's time for it to take yet another coffee bath. Backups, they let you sleep again.
Btw, defragmenting is normally not needed. People that claim otherwise are trying to pick your pocket. And it's a (usually minor) performance optimization, not something that will keep your disk from failing! On MacOS it's completely not needed, the OS does it for you invisibly. I would hope Windows (et al) do the same thing.
A couple of iffy things to do ... may not help depending on your computer:
1) When your machine is connected to power, be sure it's attached through a surge-protector, or even better, a UPS. If your computer's power supply isn't well designed, a power spike (or brown-out) can get through to your drive and cause it to write garbage on the disk. This "shouldn't" be a problem with well designed machines. Again, "shouldn't."
2) Heat. Try and be nice to your computer. If you can cook your breakfast on the case, perhaps it's not so great for the computer components inside. Again, if your system is well built, it will both crank up the fans and slow the CPU so this "shouldn't" be a worry. "Shouldn't."
3) Sleeping. Let the machine sleep when you're not using it. Avoid programs that use "idle" cycles (e.g. SETI@home) unless you understand that they're also consuming electricity and reducing the lifetime of your machine.
Hope this helps 
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