Select a dish-garden-type flowerpot with drain holes. These plants look best if you plant a group of them together in a dish garden. It needs to be only about 3 to 5 inches deep.
Fill the pot 3/4 of the way with potting soil made for cactus. You can buy this type of soil at a plant nursery or the garden center of a home improvement store. It should have 1 part sand to 2 parts soil in order for it to drain well.
Poke holes where you want the Lithops to be. Place them in the holes and cover the roots and the bottom of the plants with the soil. Stick a pencil in the soil around the plant to collapse the hole around the root.
Top with a thin layer of course sand pebbles. The plants will start to mimic the pebbles and may even be hard to find until they grow slightly larger.
Place the plants in a window that gets between 4 and 5 hours of direct or slightly filtered sun a day. Southern exposure is the best unless it will get sun all day, because that is too much sun. You may need a screen on the window during the summer to keep the plant from getting sunburned. Eastern exposure would be the next best location.
Water the Lithop. Watering a cactus is not like watering a regular house plant. The Lithop has a certain cycle it goes through and the watering must coincide with the cycle. The plant is dormant in the summer and requires very little water. You can water slightly if it is extremely dry or starts to shrivel. Water so the only top 1/2 inch of the soil gets wet.
In early to mid-August the plant will start to flower and grow again. This is when you can start to water well. Water deeply at this time to get the growth cycle started. Allow the plant to completely dry out before watering again. After the flowering, decrease watering until winter and then stop watering altogether. The plant may shrivel and that is normal, so do not remove it and do not water it.
In the spring, remove the thin shell of the old leaves and begin to water lightly again. Do shallow waterings at first and work up to deep watering a couple of times in the mid-spring. Remember to allow the soil to dry completely between watering. Then work it down to almost no water through the summer and start the cycle over.
Use a general houseplant pesticide for spider mites if you see them. You may see white lines on the leaves and not the spider mites as they are very small. Use only as much pesticide as you absolutely have to.