To maximise natural light:
Let light come through windows without interruptions. Remove secondary glazing, which absorbs light, and objects from window sills. Replace heavy curtains with blinds or muslin drapes.
Mirrors amplify light. Place a large mirror opposite the window to reflect light around the room.
Choose light and bright paint colours. Shades such as pale green, blue and lilac will make a room look larger whereas red, orange, brown and black absorb will light and make it look smaller and darker. As a rule of thumb, the lighter the paint - the closer to white - the more reflective it is.
Colours that work well in bright, hot climates such as Italy look different in grey British daylight. Terracotta, for example, looks much duller.
Your choice of flooring will affect how light a room is. Carpets are soft, absorbent and hold the light whereas floorboards with a high-gloss finish reflect it around the room.
Keep small, dark rooms bright and fresh, with as little pattern as possible. This will make the space look larger and lighter.