I've got to be honest and say this is something nobody ever taught me and I recently thought 'Goddamit, I've got to learn'. I found this clip and it's got a really clear demonstration. anyway at the risk of sounding like a spammer, here's the link. Hope it helps someone...anyone!
http://www.videojug.com/film/how-to-change-a-fuse-in-a-traditional-fuse-box
http://www.videojug.com/film/how-to-change-a-fuse-in-a-traditional-fuse-box
