Given the wide choice of different lamps and luminaires available, there is obviously an almost infinite set of different arrangements of electric lights within a room that will provide a certain illumination level. The ultimate choice of layout will invariably be an aesthetic one - achieving the right 'feel' or 'ambiance' within the space. Much of this will come with experience as a lighting designer, however, a fair bit will come from simply applying a bit of thought to the space and how it is likely to be used.
The images below demonstrate just a few of the many different ways of lighting a simple room. Each layout has its advantages as well as its disadvantages - most of which will be quite obvious even at a casual glance. The most obvious difference between them is most likely in glare potential.
Images created using ECOTECT v5 and RADIANCE.