How do you Pinch the harmonic on a guitar?

the song welcome home by Coheed and Cambria is a good example. at least i think its called pinching the harmonic, it dosesnt really make it a higher note i think, i dont really know how to explaine it. but ive played guitar for about 5 to 6 years, just kind of pittle pattled around, and im starting to get into the harder stuff. and im wanting to learn how to play this song, and i dont know how to make that sound, any help??????????