nice jumps, looks like a sweet place to ride.
in terms of picture quality, if your camera has a sport mode then straight away put it on that, it helps immensely. another thing is following the rider into the jump, so if youre the cameraman, try keep the rider in the middle of the frame, with the shutter button pushed down halfway, so that it focuses right. It looks to have been a bit of an overcast day, or maybe you just had limited light, so try bumping up the ISO a bit, and if you can force the flash on then do it. other than that, just keep practicing and youll find the picture quality and composition will improve if you keep at it.