How and why do those HDD bad blocks appear?
Is there a guide to minimize the risk of HDD becoming dead by using some proper maintenance techniques, usage or whatever?

Thanks.

Mechanical devices can go bad, even in shipment to retail.

Non-technically, the drive heads or write heads or cylinders "break"

I think Western Digital is a quality brand that I've had very good service from.

Read up about how HARD DRIVES work on their website and it's incredible, their ability, especially the manufacturing process.
It's very delicate. So the operation is enclosed in a steel box, but there still can be accidents, even just a simple "bump" to the PC. Be careful.

Just so you know. All HDD's have bad blocks when they are manufactured. You can't produced a perfect HDD and all HDD's also have what is known as a MTBF (meantime before failure rate) back in the good old days they used to place a sticker on the HDD that said it was good for so many hours till it failed, granted some are still running but all HDD's will fail at some point in time. This is why it is important to backup your data.

There is also nothing you can do to prevent a HDD from failing. The only thing you can do is backup, backup, backup. I can't say that word enough.

Later,

KTTD