You forgot to mention getting measured for a coffin if the jump doesn't go as expected.
The first thing to do is to learn the physics of jumping. The second is to find a jumping coach. Third, prepare yourself: quit alcohol and caffeine, calorie controlled diet and reflex exercise. Fourth, get all your equipment ready: grip surfaces on the launch ramp and landing ramp, tight suspension (modified from a well-balanced dirt bike with road tires inflated to 55-psig or higher) etc.
Start small and slow, then build to the stunts you hope for. Motocross jumping is a good training venue: while less than spectatular, these jumps are still high enough to kill you.
The Stunt School in Las Vegas is the best place to start.