Fix a Hanging GM Headliner

General Motors vehicles from the 1980s are plagued with sagging headliner syndrome. Here is an easy and cosmetically decent repair.

Steps

Obtain a can of spray adhesive. These are available a craft and home supply stores.
Use an old sheet or drop cloth to cover your car's upholstery.
Make a small slit in the hanging headliner with a craft or hobby knife (e.g., X-acto). It should be large enough to admit the nozzle of the spray adhesive can. If you have a large area of your headliner hanging down, you may need more than one of these.
Spray the ceiling above the area where your headliner is hanging down with the adhesive. Try to make sure you cover it well, it will be hard to go back and get areas you have missed.
Working in from the edges carefully push the headliner back into place over the area where you have applied the adhesive. It should stick pretty quickly.