Balance between front and rear brake bias is the key. There are lots of variables given the traction available, speed and angle of decent. Practice and getting to know your bike will help alot. Positioning your body weight over the bike is also just as important as to how much front and rear braking force you can apply. If your speed is too high going into a turn, then be prepared to crash no matter what.
In a downhill manuver when turning a corner, I'm always more aggressive with the rear brake than the front. I would much rather deal with the rear tire skidding than the front. Position your butt behind the seat when in a downhill manuever along with a one leg fully extended so you can brace yourself for hard braking. When going down a steep downhill manuver at slower speeds, I use as much front brake as I can without causing the back tire to lift up off the ground.
I wrecked a month ago, but I hit some loose soil going into a turn and the front washed out from underneath me. Sometimes it also helps to know the trail your riding to watch out for the problem areas.