Pics look great to me. I am trying to get ready for my sons middle school football season and need all the tips I can get.
First of all you pretty much need a DSLR and a decent telephoto lens (somewhere in the range of 200mm-400mm) if you dont have it already.
If you do here's a list of what's next...
Put it in Av/A mode at set the aperture at the lowest possible number.
Set the ISO to what's needed to get shutterspeeds around 1/800s at least (ISO 400-800 usually does it).
Set the AI to servo (what's it called on Nikons?)
Set shooting mode to continuous.
If you find it hard to get the focus right (like i do) using a narrower (bigger F-number) aperture might help. This will however make the shutterspeeds slower and also you wont be able to blur out the background as well.
Please feel free to correct me if i'm wrong and/or forgot something