If you have solid doors you can add windows or sidelights to the door to let light come in. If you have sliding glass doors those let in the most light. French doors are the next best thing and also let in a tons of natural light. If you want to brighten your living room or bedrooms and you have curtains use a shear to let the light filter through. Plantation Shutters just don’t let a lot of light in.
While I have found today’s buyers don’t like mirrors on the wall(s) and that style has fallen out of favor, you might think twice before removing a mirror wall if it is bouncing a lot of sunlight into the home. Mirrors reflect natural light further into a home.
This might sound obvious, but paint your walls white or brighter color. You can really see a different when you paint a dark wall white.
If you don’t get a lot of natural light in a room because it doesn’t have windows, you can try to add a window from above by installing a skylight or solar tube.