Tips for shooting high speed action shots w/ Rebel xt

[zachdank]

I don't know if this is the right forum to post in. I just purchased a canon rebel XT, and i am a total beginner. I've read the manuals from start to finish. I want to shoot some mountain bike action shots. I was wondering what would be the best settings to use for this. I've taken a handfull of shots, but i know i have a long way to go. I want a crisp clear subject. Nothing abstract or streaky. Don't know the terms that you guys use to describe these things. Here are a couple of shots that i have taken. I'm not happy with them.
Thanks for the help in advance.
Like i said, I'm a total beginner with little knollege of digital cameras.