I'm new to all this fancy photography and am having trouble getting my setting just right for photographing my son's hockey games.

I'm gettting about 1 out of 8 pictures that come out just ok. I was getting some better shots, but I think I changed some settings.

My question to any expert out there is what are the correct settings on my Canon Rebel XT 350D that would give me the best pictures. I am using a 75-300mm lens as well. Any help would be greatly appreciated.

Current Settings:

Tv
Shutter Speed = 250
ISO = 800
AF Mode = AI Servo
White Balance = Flourescent

Pictures are a bit grainy and not very focused.

Thanks for any help!!