“Mirrors can make a space feel brighter because they bounce the light around the room”. But placing one in the wrong spot can be almost as bad as not having one at all. Put mirrors on walls perpendicular to windows, not directly across from them. Hanging a mirror directly opposite a window can actually bounce the light right back out the window.
Stick to colors like beige or gray, especially on the first floor, where flow is important. Neutral walls give you the greatest decorating flexibility, allowing you to easily switch up your accessories. And if you have two small rooms next to each other, painting them the same neutral color helps them feel larger.