Most of the basics have been covered; lots of good suggestions so far. Lowering your center of gravity on a descent is good, so lower your seat. If you don't have a quick release seat post binder that can be a pain to deal with, though easily purchased. To me the ideal is an adjustable seat post like a Gravity Dropper that you can use to lower and raise your seat with a handlebar control while riding. Another thing, even if you ride a full suspension, don't forget to use your arms and legs to help out and to move your body to flow with the terrain somewhat. Don't forget your front brake is your more powerful one, just use it wisely. You don't have to go as fast as possible all the time, either.