The quickest easiest way is to just pound a nail through the platter. Most platters are glass and will shatter, the metal platters will break as well. I've destroyed my share of drives. Sure you can run software, write zeros, etc. But physical damage is insurance. I like to take them apart to get the magnets out of them.... depending on the drive the magnets can be very powerful.
If you are going to physically destroy it you should wear safety glasses as it's not uncommon for little pieces to go flying everywhere.
If it's a Hitachi... they destroy themselves... just install a new OS and turn on your computer... they don't call them Death Stars for nothing. :)