I spent some time photographing my son and two friends at a skateboard park yesterday. I am not happy with the results. Besides images specifically for stock, I mostly enjoy nature photography and I am not experienced with sports/action photography. I am going to describe what I did yesterday. Can anyone offer advice as to what I should do differently?

I was using a Rebel XT and a Sigma 24-70 f2.8 lens. In Aperture Priority I set to f/5. I used ISO 100. I used AI Servo focus mode. I then followed the skater until he was at the spot or pose I wanted and took the shot. This gave me a SS of about 1/1000. Occasionally it would drop to 1/800 which was not fast enough. I then went up to ISO 200 and this was fine for the needed SS. I also tried opening up the lens more for some shots and left it on ISO 100. Also tried single shot focus mode, pre focused and a particular spot, and waited for the skater to skate into the frame. This did not work well for me because the skater was not always in the best position or best skating trick at that exact spot.

Maybe I would have been better off in Shutter Priority mode with a set SS of around 1/1200 or so? How do others approach this type of shooting? I would appreciate any help or advice.

I should have said what was wrong in the original post. About 60% were trashed due to being out of focus.  Some of these were really focus problems and some were because the SS went a little too low. Of the others, about 1/2 were poorly composed. This was due to trying to follow the action and press the shutter button at the right time. I ended up with hands sometimes chopped off or the front of the skateboard and feet chopped off.

In general, I am curious how others go about shooting in these types of environments. What type of focusing do you use? Is AI Servo best? If you plan on submitting these for stock, What ISO do you use? Do you use Aperture priority or Shutter priority? Do you open the lens as wide as possible and use ISO 100 or shoot at a higher ISO and get a little more DOF with a smaller aperture?

I've never shot skateboarding (now there's an idea) but I've done other sports ... skiing, cycling, triathlon and, just yesterday, Swiss wrestling.

I think the first thing you have to accept is that a far, far higher proportion of your shots are going to be duds. Much higher than, say, with landscape photography. If I get 1 out of 25 useable images in fast-moving sports shots I'm deliriously happy.

The second thing that I try to do is to identify the moment and precise spot when I want to capture the image. (I would guess, with skateboarding that could be at the top of a jump.)  I pre-focus, manually, on that spot.

I then follow the action through and press the shutter a fraction before my subject reaches that spot. It's impossible to say how to do this. It's an art. But I have improved a lot with practice.

Interestingly, once, with ski-jumping, I tried the continuous mode on my camera, holding the shutter down at the beginning of the action and whipping off shots. But I quickly gave up on that. Even though it was taking 3 shots a second, it usually missed the crucial point and I got a lot of skiers too small, half-skiers, or empty frames. There's nothing like the human eye for accuracy.

Great tips!  yingyang0 has done this before and knows skating!  I'll take it one step further.. take the advice of getting down, that's laying down to get shots from a smaller pipe to start.
Then, once you're comfortable..  MOVE CLOSER.  It's one of the more important tips we teach our photographers here...  push yourself, your photography ...and your subjects.  Nothing beats a great in-your-face action shot.

Good luck.  JC

(PS. I wasn't kidding...  loose boards do hurt!)