Purchase lithops plants from your local nursery. Since these plants have such specific watering requirements, you'll want to keep them in a container. It's also good to keep your lithops separate from other cacti in your collection until you've figured out their care requirements.
Place a thin layer of stones on the bottom of your planter. This helps the water drain out of the soil. Then fill the container with cactus potting soil. Using your finger, poke holes in the soil large enough to fit your lithops plants. Remove the lithops form their containers and place them in the holes, then cover up any remaining space. Top the container garden with a small bed of stones to showcase the plants' natural resemblance. Water the lithops after planting to allow the soil to pack around the plants' roots.
Place the plants in a location where they'll receive indirect sunlight if they've been inside at a garden center. The plants will need full sun, but you'll want to introduce it slowly. If you're planning on keeping the plants outside, move them into direct sun after three to five days. If you are keeping them inside, place them near a window that offers sunlight, and add a plant light for additional light source if necessary.
Water lithops only when they begin to shrivel during summer months. Summer is their dormant season. They will begin to grow sometime in August. This means you'll switch to increased waterings for the early fall before tapering off again.
Water deeply from August to late September to mimic the rainy seasons of the lithops' native Africa. Water the plant thoroughly before letting the soil dry out again. Stop watering your lithops altogether in late September. If you live in a hot climate and plan to leave your lithops outside, move them somewhere they won't get wet.
Do not water them during winter months. Move indoor plants away from windows to avoid drafts. You will notice them shriveling; underneath, new lithops plants are developing from the nutrients of the old. When the plants have dried out to a papery mass, remove the thin, papery shell of the old plants to find the new plants. At this time you can begin watering sparsely.
Increase watering so that the plants are receiving heavy soakings in the springtime. Decrease again for the dormant summer period.