When entering steeper slopes try to keep your weight centred over the cranks by extending your arms and pushing the bike into the descent whilst moving your body back and down in one smooth motion. Maintain your ideal 'loose hands' riding position with your weight over the cranks as you continue down the slope.
Stay over the cranks.
If you go any further back and hang off the bars you are taking too much weight off the front wheel which will result in poor steering and unpredictable braking. Too far forward and the rear wheel may lift sending you over the bars.
Drop both you heels and use your leading foot to help brace against any forward movement.
Try not to drag your brakes all the way down a long descent. Brake firmly on smoother, less steep sections of trail allowing the bike to roll through rougher and steep sections if possible.
When descending, bear in mind takes much longer to slow down downhill so ride accordingly by braking earlier than you would on the flatl.
When braking, anticipate the extra push forward on your body as you would on the flat moving even further back and down to avoid putting too much weight on the front end. Remember to bring your weight back forward when you release the brakes again.
At the bottom.
As you approach the bottom of the slopecheck to see how quickly it levels off. You will need to adjust your riding position bringing your weight forward as the trail levels off to make sure you don't loop out off the back of the bike.
Move your weight slowly if the trail transitions from downhill to level over a long distance and quicker if it has a short transition. The aim is to keep your weight over the cranks.
At faster exit speeds you will feel your body being pushed down into the trail. This is called G-out. Try to compensate for G-out evenly with your arms and legs without moving your bodyweight backwards. This will require a little weight on your handlebars.
If you try to compensate just with your legs it will put your weight too far towards the rear of the bike again leading to a possible trip off the back of the bike.