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You have a good start here.
The one thing about skateboarding photography is that it's about perspective. Unlike traditional sports photography where you can have a tightly cropped subject and the story of the photograph is in the action itself, skate photography doesn't always work that way.
If you are familiar with this famous photograph, you see the story isn't the action of shooting a three pointer itself. The story in this photo is told because of perspective. You can see that the period is it's final seconds (you don't know if this is the end of the game or not) because he shot clock and you see the face of the crowd all on the action, generally meaning that it's a close game.
The story in skate photography is told the same way and most successful skate photographs contain the following elements:
* The photographer is either extremely close to the subject with a very wide lens, often a fish-eye, or
* The photographer is farther away with a lens in the range of 35mm to 50mm (on a full frame camera).
(* Telephoto lens can also be used, often when it's harder to get closer to the subject, but the perspective part is just as important.)
Unless you are in the former (wide-angle lens), you should consider shooting with a tripod (at least to start) to get your composition set and then allow the skater to come to you. That doesn't always work when you're dealing with a free-for-all skate park environment.
I don't have as much to reply as I thought when I started, but keep in mind that with most rail tricks and many tricks in the air over any kind of terrain obstacle needs to show a minimum of the starting point and move being performed or the move being performed and the ending point and hopefully all three.
Paul can help you learn more about how to best utilize off-camera lighting to enhance your subjects but keep in mind that in some cases, the skater is just a very small portion of the overall composition.
See this snowboarding image:
Hope this helps.