If you would like to freeze the motion of the subject along with the motion of the background, you should use a very high shutter speed. Normally this shutter speed is at least 1/300th of a second in order to make sure that you freeze everything. But there are other subjects you might find that will be moving unusually fast such as cars or thrown objects. If you would like to freeze a faster moving object you will probably need to use a shutter speed closer to 1/1000th of a second or faster. This shouldn't be a problem now because the new cameras are coming out with shutter speeds of up to 1/8000th of a second.

Leo Matiz