Protecting external hard drives?

I have to external hard drives by WD. Each is a 3 TB. I notice once makes a little sound which worries me. It's the one I have hooked up to my iMac's Time Machine.
What is the best way to protect these external hard drives? I would guess to not keep them on all the time? What is the best way to eject them and then find them again with the Finder?
Thanks for your help

There are differing opinions about keeping external hard drives attached at all times. One advantage of keeping them attached is that Time Machine will constantly make updates that way. The disadvantage is that the drive is always working - spinning up and spinning down. More wear and tear.

I personally do not keep my external drives attached at all times and only hook them up for backups (Time Machine or Carbon Copy Cloner) and when I need them for data.