How do you repair a 2000 Pontiac grand prix passenger window that has fallen off its track?

There are guides that clip on the glass, one is on the upper rear of the glass,and the is on the lower front. Most of the time the one on the rear breaks causing the window glass to tip forward. You can remove the old clip & install the new while the glass is out of the track.And then reinstall the window by seating it back in the channel.