To be able to properly shoot action sports there is one thing really important that has nothing to do with photography itself. That is understanding the sport you are shooting.
All these action sports (skateboarding, snowboarding, bmx, etc.) have a culture around them that you have to know to succeed in representing them properly. You need to know the right moment when a certain trick has to be shot, or if a frontside boardslide has to be shot from one side or the other, etc. All these things can be learnt by immersing yourself in the sport, the culture. Buy mags about that sport and study the pictures. Watch videos to understand the tricks. Talk to the athletes, show interest in their sport and they’ll help you understand it. They all love to have good pics of them taken. Even better, try the sport for yourself, it’ll make you completely understand it and respect the athletes even more.
This single aspect can make your photography improve drastically. If you want to make a living shooting a certain sport then this concept is basic. You won’t get a single picture published in a specialized media unless you do understand the sport.
Outside of that sport niche things are a bit different. Once you get into it, you’ll start to notice that the action sports pictures on mass media are usually shot by photographers that don’t know the medium. You can tell right away. I hope companies and ad agencies start to understand this and begin to get the right photographer for the right job.
Meanwhile make your homework and start learning!