You've reached the top. Well done! Now the fun part starts. The down! No matter how fast or slow you like to descend, the most important part is to stay on the bike. Descending safely is much more preferable than hurting your body. Face planting and A over T'ing is painful.

First things first, you need to change to a bigger gear once you're at the top of a hill. This is a good time to change the front gear.

Line Choice

Scan the trail about 10 metres ahead and choose your line as you head down the hill. Line choice is by far the most important part of descending, in fact, it's the most important part of MTB riding. It can make the difference between a fun descent and one where you have to tackle terrain you're not ready for.

Braking

Just in case you need to slow down, let your fingers cover the brake levers. If you do use the brakes, be careful not to go too hard on them as you really don't want to lock up the wheels, especially the front wheel. The front brake is much more effective and if you brake too hard, you'll end up being tipped straight over the handlebars. This really isn't a nice experience, so better not to do it. Instead, ease on or feather the front brake if you do need to slow down.

Out of the Saddle

If it's any type of decent downhill, you'll need to move your weight backward behind the saddle. Why? To redistribute weight over the back wheel which then means you're less likely to be thrown over the handlebars. Again, this is not a fun experience! How? By standing up on the pedals, lifting your butt off the saddle and pushing yourself backwards a little. On really steep descents, you might even need to move yourself so far back that your butt is almost touching the rear wheel!

Rarely will you see a good rider sit on the saddle on a downhill. Being dynamic on the saddle means you let the bike do what it needs to as it rolls down. If the bike has enough speed, it naturally wants to stay upright as long as you let it or as long as you don't pick a stupid line. Try it!