First thing you need to decide when shooting a moving subject is what is the motion effect you'd like to capture in your image. If you'd like to freeze the motion you need a short exposure. If you rather depict the sense of motion by creating a motion blur, then you need a long exposure.

Note that short and long are relative to the perpendicular (tangential, i.e., across the image) speed of the subject. So, you can see that the important factor here is exposure time, or shutter speed, and this is controlled with the Tv (Time Value) semi-auto mode. Once you set the desired exposure time, the camera will determine the required aperture (Av) automatically to get a correct exposure.

{Note that you can also use the M (Manual) mode to control both aperture and shutter speed independently, if the auto exposure result is not to your liking. Alternatively, you can use exposure compensation (AEC) to get that with the semi-auto modes.}

You can then add some artistic effects by using your flash. With the flash set to 2nd curtain exposure, you can freeze the subject at some instant and get a nice trail of blurred image. This will give the viewer the sens of the motion and its direction.

Regarding the other settings, generally speaking you should set your ISO to the lowest setting that will let you achieve the desired output. This will get you the highest quality in terms of digital noise. The focal length should be set such that you get the desired composition for your image, regardless of the other parameters.

UPDATE: In response to @mattdm's comment - personally, I use autofocus mode almost exclusively. The exceptions are when shooting in a low light, which does not allow the AF to lock-on, and when doing "studio" work, mostly with still subjects and on a tripod, where I can set the focus point to a specific place and leave it there.