How to SCREAM without killing vocal chords?

I'm a "freak" in that I can scream naturally and not hurt my voice at all but I do NOT encourage it in others. All of the above comments are right, you do not want to damage one of your instruments and if the director insists that you really, really scream they are not worthy of the title. In the productions where my character has been required to scream and I've done it for the first time at rehearsal the directors have all fallen off their chairs to get me to stop, when they've realised I'm not hurting myself they almost cry (I hope with joy). It's very unsettling for an audience, they really can hear the difference... but I repeat, I am a freak and very lucky. DONT DO IT WITHOUT WARMING UP and relax your throat, tilt back your head, relax your jaw, tighten your diaphragm and scream from there. Visualise the sound from the pit of your stomach, support it from the diaphragm and let go. Be very, very careful. Rapunzel "there's no respect...."