Hang your mirror at eye level vertically if it’s rectangular in shape. That way, the mirror runs along the top of your couch.
Install a floating shelf on your wall, a few inches below the bottom edge of the mirror. Choose a shelf that is approximately the same length as your mirror. This will serve to anchor your mirror, much like a fireplace mantel would.
Add accents to the left and right side of your mirror. These could be sconces, candelabras, or even smaller, matching mirrors. Leave as much room between the side edges of your mirror and your accents as you did between the bottom edge of your mirror and your floating shelf. This creates uniformity, while also drawing the eye to your mirror.
Pay attention to natural light reflected in the mirror. Open your blinds, at least partially, to let in some light, which will be reflected in the mirror and make your room feel big and warm. Dress up your window. Because visitors will now essentially look at your window twice -- once at the window itself and once at the window as reflected in your mirror -- you want it to be a decorating asset to the room.
Add lighting strategically around the room so that it’s reflected in the mirror. This will help brighten up the room drastically.