basic rules are:
if you are on a high speed track - set your brake bias forwards
if you on a slow speed track - set it backwards a bit
itis all about 'the balance'
if you are suffering from oversteer, then DONT set the brake bias rearwards as you will not transfer the weight of the car to the front as much and will only highten the oversteer.
and vice versa.
just play with it.