Many gardeners who read this blog know far more about the mysteries of the Lithops than I do. They can ignore this post. But for those of you who have recently bought, or been given, some Lithops, I thought I'd post on some of the basics that I've learned over the last couple of years. Feel free to add useful advice in the comments section!
Apart from the initial re-potting, Lithops don't like being repotted or moved around much. In fact, such things can lead to Lithops Mush Syndrome. They grow slowly, so repotting is seldom necessary anyway.
Now on to watering. They don't like it much. I water weekly during their growing season. I never let them sit in water for even a few minutes. I do water very lightly during their dormant season, just a few drops from a water dropper every 10 days or so. But many gardeners don't water their Lithops at all during the dormant season. So it's up to you. I have very hard water here, so I add 6 drops of rice vinegar to every liter of water. I also add one drop of cactus fertilizer to each liter of water.
You might ask how to know the growing from the dormant season. This is a complicated subject, and if you check out the link below, there is a website with a wonderful explanation, and it's illustrated!
As far as sun goes, Lithops growing in the ground like, and can handle, a whole lot of full sun and heat. But in pots, too much sun, and especially, too much heat will cook them into mush very quickly. Also, if Lithops don't get full sun normally, then are put out on a sunny, hot day for even an hour, they'll often fade (Lithops sunburn) and turn to mush a few days later. I speak from early, bitter experience on this one.
Here is a terrific German website with in-depth explanations and pictures:
Happy Gardening, everyone!