Some instructions on how to use jumper cables are wrong if you drive an older (stupid) car. My mom had an old Ford before and lost polarity on the alternator (basically frying it... wouldn't harge the battery after that) simply because she connected the black cable to the negative terminal. The tech said to never do that and always just connect the black cable to the frame or whatever.
I never use the negative terminal when using jumper cables because of this and I've never had an alternator problem myself.
Just broke my personal record for number of consecutive days without dying!