To copy an icon from file/folder/hard drive to another:


Get Info for the item whose icon you wish to copy: click the item and type command (clover-key)-I, or right-click and select Get Info

Click the icon at the top of the Info window. A grey outline should appear around the icon. 

Now copy the icon: type command-C

Close the Info window.

Click the item whose icon you wish to change, and Get Info on that.

Click the icon at the top of the Info window. A grey outline should appear around the icon. 

Now paste the new icon: type command-V

Close that Info window.