Dug up this awesome quicktime video on Artificial or pinch harmonics..
Its kinda hard to put it in words but watch the video and you will get it.
Its the first cool trick people learn.. You can make ur ax scream with it.
Download Video Here
Some songs using it-
1.Peruvian Skies- Dream Theater
2. Hells Wrath (living through me) - Pantera
PS- You need a electric with high gain and distortion to do it properly