You're just using the kit lens, right? Chances are, you won't be able to freeze action with it. I know I'm shooting Canon, but the kit lens with the Rebel just won't do that, it's not fast enough. What kind of lens is it, exactly?

My action lens is a f/1.8, I tend to have it around f/2-2.5 when I'm shooting action (most lenses are not completely sharp when they are wide open - which is the lowest f-stop they can get to. In this case, my lens can get to 1.8). Typically you should have your shutter speed around 1/1000 but depending on how fast your subject is moving you may be able to get away with a smaller number.

Bumping the ISO up alone will probably not get you a very sharp picture. But like Catlady mentioned, when you speed up your shutter you will need to open up your f-stop. Speeding up the shutter will make your pictures darker, and then in turn you will need to open up your f-stop to let in more light. But, this causes you to have a very shallow depth of field. Unfortunately this makes it hard to get the shot because it is hard to focus fast enough to get, say, the dog's face in focus. There are lots of shots I have with the dogs coming at me at full speed and I have their chests in focus because I just couldn't focus and click fast enough. This is what makes actions shots so difficult and, for many photographers, so desirable. However I must say shooting humans vs. 4-legged animals is much easier because you have much less depth to a person vs. a dog or cat who is coming at you.

I'm the same way though - I like the action to be frozen totally and everything in focus. I hate it even when I get a shot that is totally in focus except for a foot or something.

By the way, feel free to PM me if you have any questions. I won't be able to help you with things specific to Nikon but I can help you with settings and such if you'd like.

And also, I think these are a really, really great start. I don't know if I ever got pictures that sharp from my kit lens, though I'm not sure how mine compares to Nikon's. It wasn't until I got a better lens and learned how to have control of my settings that I started getting sharp action shots. And I'm still not satisfied - I'm totally eyeing an L glass lens, but seeing as it is over $1,000, it will be a while before I can get it! I'm looking to sell some equipment soon to figure out a way to pay for it though, haha.