Light: Lithops requires full to very bright sun (either direct or indirect). Shade will kill this plant! It can take full strength sun, but be mindful of sun burning the leaves (I know this from personal experience). If your plant is in full sun, be sure to water every week (instead of every two--see below).
A window facing West, South or East should do nicely. Too much light is not a problem for Living Stones. Too little light is! If the plant appears to be 'reaching' for the window or light source, it needs more light! Stretching will cause the Living Stones to lose their rock like appearance and grow taller. If this begins happening, simply find another place with more light.
In the wintertime during active growth, you may want to move Living Stones closer to a window – they need as much light as possible when producing new leaves. The rest of the year, they still need sufficient light, but even if they aren’t right next to a window, be sure they can get some bright sunlight. Where you place your plants really depends on your window access (a house may have several whereas an apartment or other place may have only one or two) and your available space for plants. If you’re already obsessed with plants, the chances are good your space may be limited! The good news is: Living Stones tend to be small kept singly or in clusters. Plants grow slowly and don’t need huge pots or containers. If your plant space is limited, Living Stones may be a plant for you!