This question has no easy answer, as opinions on this subject vary greatly. However, a good rule of thumb is to take the height of the ceiling and divide it in half. This is the distance that each light should be from one another. For example, a room with an 8' ceiling, should have lights approximately 4' from one another (8' ceiling / 2 = 4' apart). The total number of lights will also be affected by the type and wattage of the bulb being used. Spotlights with narrow beams will produce pockets or pools of light, while flood type bulbs will produce broader amounts of light.