Answer:
If you have drum brakes, you need to remove the drums and adjust the star wheel that expands the rear shoes, compensating for wear. On my van, I adjust them whenever I rotate the tires. To remove the drums, you may need a pair of metric bolts that fit the jacking holes that are drilled and tapped in the drums. By removing the drums, you can inspect the brake shoes for wear and replace when necessary.
You can also adjust the rear shoes via the adjustment holes in the rear brake mounting plates. Remove the wheels and secure on jack stands. Make sure to chock the front wheels, as you will have to disengage the parking brake to test brake tension. with a small screw driver the adjust the star wheel, located directly under the caliper piston housing. Tighten it until the first sign of drag on the drums.
There has been some discussion that the drums will self adjust when backing and applying the brakes. Also I have seen mention that applying the parking brake 5 times in succession will cause self adjustment. I apply the parking brake every time I leave the car, and I back out of the driveway and brake every time I leave the house, however, every time I have replaced front pads the rears need major adjustment.