Think about grip point, ie brake and turn where there is plenty of grip. Where there is little grip, say roots and rocks, try and keep the bike light. Speed is definately your friend.
I once saw Gee Atherton ride in Wales, his wheels didnt touch the ground…
Also, since ive been getting up to huge speeds on my road bike down some hills, this transferrs well onto the DH bike. When riding DH i dont really feel that im going that fast in comparison. Like motocross and huge jumps, although i dont ride motocross so im assuming.