Repaint walls with a light color, such as pale yellow, light gray or powder blue. Use an eggshell, semi-gloss or glossy sheen that will reflect light rather than absorb it like a flat paint does. If you prefer darker colors, save it for the trim.
Cover dark floors with light-colored area rugs. Ask the landlord if he or you can redo the flooring, such as by installing white tile in the bathroom and kitchen, installing light carpeting or refinishing a dark wood floor to a lighter finish.
Avoid dark wood furniture. Cover dark tables with a bright tablecloth. Use slipcovers over dark couches and chairs. If you want to use darker colors, do so through accessories such as throw pillows to create contrast.
Hang a large mirror in each room -- this will reflect artificial light and indirect light from any windows.
Clean the window panes and use window coverings that are light in color and light in weight. A sheer or lace curtain works well in a dark room. Then, place a fresh or dried floral display or a plant on the center of window sill if it is deep enough.
Add extra lamps in the room to compensate for the lack of sunlight. Place a table lamp on each table in the bedroom and living room. Add a floor lamp with a halogen bulb that can brighten up the ceiling and top half of the room. Add a lamp to the dresser and other large pieces of furniture in the apartment.