Originally Posted by minnow11
use a tornado drywall anchor, they are rated for 75lbs and are easy to install. They are available at pretty much all hardware stores. They are the plastic things that look like tornadoes with a phillips screw head. Make a small hole and just screw it in, hang mirror on screw or hanger screwed in to the anchor.
These work great if you are going just into dry wall sans studs