All aids off - including Traction Control (you can't power on 'oversteer' with TC on)
By far the biggest improvement in my game came when I turned off TC (even setting 1 is a big issue on anything but the F1 cars) and learned to brake earlier/less, and try and power through the corner with the accelerator.
As little steering input as possible and carry as much momentum as possible. On the tight corners exit speed is MUCH more important than entry speed.
If I was in front of my GT5 I could give you more tips.... I JUST did these but having a hard time remembering which is the 3rd sector.