A wider aperture e.g. f2.8 would give you a narrow depth of field - less in focus, not the other way around

Using your flash in Second curtain Sync mode can give an awesome effect to panning shots. Because the flash fires at the end not the beggining of the shot. This means that rather the rider being frozen at the beggining and blurring forwards (Effectively making him look like he's moving backwards) the frozen rider is at the end of the blur, increasing the look of speed and still getting a sharp subject

You should be able to tell if its your focus or your panning that is off. As a properly panned shot will have a pin sharp subject. If its not in focus everything will be out of whack.

thats the one!