Sounds obvious,but people still do it. Stay off the brakes and pedal real smooth over wet rocks and roots ect.
If you are on a downhill try to scrub alot of speed in a good spot and fly through the rest. Being on the brakes slows your suspension and puts lots of weight on the front wheel.(endo concern) If is is real slippery you can use the sides of roots and rocks to bounce yourself in the right direction, but watch the sidewalls.