How can i train my voice so i can scream like slipknot?

How can I train my voice so I can scream like slipknot?
I have A show really soon and I need this answered soon.
Every time I try to do the yell I pass out or get light headed.

erm i dunno actully,i just do it lol,
take a deep breath in tighting your throut and scream from the bottem of your guts.

You may have heard this before but just use your diaphram. It sounds like you are emptying your lungs completely, which is why you pass out (lack of oxygen). If you hold your abbs in when you are screaming then you can get more force without having to use all your breath.

get singing lessons and the way they make u sing will help u
honestly it helps me

thats sh*t. u can't really. it's his voice

Thanks the show went great I got it downpat now

Make sure you have plenty of saliva at the back of your throat, but not so your breathing way is blocked. Similarly make sure you have no phlem.
Start out with whispering with saliva at the back of the throat, to practice and make your voice crackly.
As you get used to the feeling try different styles by narrowing or opening your throat more.
Avoid closing your throat up too much. You can hurt your throat this way.
Move the shape of your mouth. It adjusts the tone. Experiment with different shapes.
Practice. Eventually you will get used to the feeling and can explore different types of screamo used by different bands like; Swing Kids, Bullet for My Valentine, Orchid, Saetia, The Used, 36 Crazyfists, S.O.A.D, Escape the Fate and possibly my favorite screamo type bands Atreyu/Enter Shikari, Bring Me The Horizon, Brokencyde, Alesana, and Underoath for a good crunk feel.