Hands-down, the Lithops (also known as a "Living Stone") is definitely one of our cooler succulents. From their alien-like patterns, to their odd colours, to the frankly WEIRD way they grow, they are absolute attention-getters, no matter where they are placed.
Water: Soil should completely dry out between waterings. Always ensure that excess water is able to drain away to avoid rot. Avoid watering while new leaves are appearing.
Light: Butt Plants need lots of bright, indirect sunlight in order to thrive. While they can handle some direct sunlight, too much can lead to severe damage and sunburn.
Soil: A light, well draining potting soil is best.
Humidity: These plants are not the biggest fans of humidity. You can mist on occasion, but not too often. Keep away from excess humidity or moisture.
Fertilizer: Fertilizing these plants is not required.
NOTE: As tempting as it may be to try and peel/remove the old leaves off of the new leaves, try to avoid temptation and leave those leaves be! The lithops wants to reabsorb as much as it can from the old/dying leaves, and removing them too soon can reduce the nutrients it needs, and could hurt, or even kill the plant. Only when the old leaves are reduced to dried, crinkly, discarded skins can you try to gently (gently!) remove them from the pot.