Some of my brothers old rules off the top of my head (ex top 10 youth/junior national rider)
* Switch your mind off
* Always be looking for your entry, apex and exit.
* Pedal less, pump the terrain more
* Keep low over jumps when you can
* Don't look at stuff you don't want to impact at high speed.
* Riding on your limit and crashing a lot eventually improves your speed, if you don't give yourself a major injury and then lose your confidence.
* Flow, the fastest line through one section might mean your much slower in the next section.
* Weight up the wheel you need the most grip with (learn to really drive the tyres and get a feel for the edge of their grip)
* Take up BMX/Trials/Dirt Jumping/Street riding to improve your bike handling skills when not on a downhill track. Get used to going big.
* Do some motocross riding to get used to going at silly speeds.
* Follow faster riders, but they may actually be crap...but just better than you. Find your own fast way down if you can.
* Practice. Practice. Practice and then practice some more. You need a full range of bike handling skills that you can call on unconsciously.
* Ride with some aggression.
You most likely won't develop a lot of this because you need to be young and have that sense of invincibility to do so.