It's done through a combination of cranes and winches. In the photos I just posted of the Millennium Force construction (
http://www.guidetothepoint.com/thepoint/gallery/default.asp?section=mf ) there are several shots in one stage. Also, if you check out the time-lapse video clip, you can see the car being pulled over the first hill and through the first turn.
In those photos on the gallery link above, you'll see one photo where the bumper on the front of the car has been replaced with a hook, where the cables are attached. The car is always secured to the crane or the track from the front or back, so it's a pretty slow, boring process.
Keep in mind that they don't do the entire train at one time, which would be rather heavy to be maneuvering about.
-------------
Jeff
Webmaster/Admin - CoasterBuzz.com