Originally Posted by
merlinextraligh
^
not using flash, I'd definitely shoot in shutter priority when panning for a motion effect.
Use caution with this method depending on how much motion you want to show. If you are looking to show a lot of motion with a really slow shutter, you aperture will possibly be at the minimum opening and it may not be closed down enough to give proper exposure. If you do find you are at the limit, switching to aperture priority and controlling the aperture opening will give more consistent exposure without the worry of underexposing.