As a rule of thumb, mount wall lights so the centre of the fitting sits about 150 to 170 cm above the floor, roughly eye level. Beside a bed, drop that to 120 to 150 cm, or just above the headboard, so the light falls on your book rather than your eyes. In hallways, space fittings 2.5 to 3 metres apart for an even wash of light. Always confirm positions before your electrician roughs in the wiring.