How does one properly clean spark plugs. What tools or materials are needed? THANKS

This is not the answer you wanted but I use to be an Aircraft mechanic and we had a small machine that did it all :Dfor us.

We just screwed a plug into it and switched it on. It sandblasted the plug and looked brand new afterwards.

Then all we had to do was check/adjust the gap.

Crazy why so many guys just replace plugs when in an aircraft which flies in the sky, they re-use them.

i usually use sandpaper :D

sure its not the right way,but i soak them in gas overnight and then use sandpaper

I'm one of those guys that replaces them, at least on newer cars. Platinum tipped plugs can't really be "cleaned" well and in fact the coating seems to go bad slowly which is why you have to eventually replace them: of course they go for at least 40K miles in some cars (Porsche) and 100K in others, but I don't wqant to take the chance, so I just replace them.
I also sometimes use octane booster, which turns the plug tips a sort of orange and is harder on them (even platinum) but the extra power is worth it.

In 60s and 70s cars I just clean them: sand them as I can (including down inside) with 180 grit, then use a hard brush to clean the threads, then soak them in gasoline, the use sanpaper again, then blow dry them with the compressor, and finally gap them.

I sandblast them to get them like new
if they are really shot then replace them

sandblasing works great. I have a blasting box in my shop. blast'em inspect the electrode if it's worn, rounded, or excessively burned replace it. Don't use them if the porcilian is cracked.