Just scream at the top of your lungs...not like a girl, though.
Your vocal cords will undergo some serious damage, and at first you'll barely be able to speak. But the scarring will allow for such vocals to become more natural, so to speak.
Just make sure you don't go about it half-assed-ly, because that's what does the most damage. Realize your range, straining past your limits can cause damage. Abbath did well within his limits, not everyone can scream as piercingly as Hat (from early Gorgoroth), for example. The power comes from within the torso--it is actually quite therapeutic, you'll come to find. Unfortunately, in college there aren't very many places where one can be alone...though I do some growls when I'm alone on the elevator! hahaha!