1. Only do this stuff because you want to, don't do it to impress your mates. Better still, find some like minded mates.
2. Get professional advice or training for your first attempt at extreme activities.
3. Always wear the best helmet and body armour you can get your hand on, and replace it when it gets damaged. And make sure you wear it, its no good having a crash and your best helmet is at home.
4. When going out training, let someone know where you are going, its a real bummer lying in the woods with a busted leg and nobody knows where you are.
5. Do not do this stuff in a public place, injuring yourself is one thing, maiming the general public is not cool.
6. Keep fit, your body will withstand crashes better and repair faster if you are in good shape.

So far I have broken both collar bones, one wrist, one ankle, a few ribs, and my tail bone. I've had a total of 53 stitches in 6 places, plus lots of friction burns caused by sliding up the road.

But my helmet and safety gear
came off a lot worse and I'm
still here to tell tell the tale.