I've done a lot of research on growing Lithops and Conophytum so I figured I would share what I've put together. This information comes from many different sources and I've tried to take what was repeated most often as being most effective. If there is anything you don't agree with or any suggestions you have, just let me know.
The information here is specific to Lithops but also applies to Conophytum. The only difference is that Conophytum do not have a dormant cycle. Please take a look around for more information. I have not grown Lithops from seed before so I don't know how these methods will work.
Update: I am now growing both Lithops and Conophytum from seeds.
Native to South Africa and Namibia.
They experience hot summers (at which time they become dormant) and cooler winters.
Rainfall varies greatly across the habitat but is generally extremely low in the summer.
Flowers & Seeds:
Single, daisy-like flower between two leaves, lasts about a week.
It is most fertile on day 4, make sure not to wet as it destroys pollen.
Capsules should develop within a few days.
Don't remove these until entirely dry (usually after old leaves have died new leaves have emerged).
If capsule gets wet it may open and seeds will be lost.
Carefully cut off capsule without damaging plant.
Rub between water or moisten to release seeds.
Germinating & Early Care:
Need good ventilation and warmth, but too much heat will cause dormancy.
Best results seem to be with a cool night/warm day temperature cycle.
The seeds are extremely small so a piece of paper may be used to scatter evenly.
A 10cm pot can hold 20-80 seedlings.
Mainly mineral based mixture, little organic matter, max size 3mm if possible.
I will try putting a mature mix beneath say 2cm of germinating mix (see later for mature mix).
The seedlings tend to grow up and out of the mix unless it is really porous but this mix won't work well for mature plants.
Sprinkle a little bit of sand on top but just barely enough to cover the seeds.
The first sprouts can be expected in a week.
For next three weeks keep soil damp but never wet.
Spray with a mister in the afternoon and morning to prevent watering disturbances (seedlings are tiny!).
Should be well developed after 3-4 weeks with reddish tinge, begin to reduce watering.
In 3-4 months should begin first leaf renewal (original leaves will shrivel, after a few months new ones will burst out.
Best to leave them together in sowing pot for up to two years until established (they don't like being disturbed, and this is why I'll put a mature mixture underneath).
25% decomposed granite or pumice, 50% Compost, 25% sharp sand
4 Parts fine river sand, 4 parts coarse river sand, 4 parts sieved compost, 1 perlite, 1 vermiculite, 1 coconut fibre (just leave out the coconut fibre if you're not in the tropics and don't regularly eat coconut and save the husks).
Anything works but will obviously affect watering.
Make sure to use a minimum depth of 10cm because they have deep roots for their size.
Every two years is recommended to renew the soil.
Best time is after new leaves are visible and old leaves are completely dry.
After they bloom in October/November mist every other week (after they go dormant, simulates natural humidity and low rain).
When active growth resumes in late spring water about once per week until summer.
Plants may go dormant in heat, water no more than every three weeks.
During active growth, if leaves start to retract into soil or wrinkle, it needs watering.
Give a good soaking (during active growth) a lot of times people only moisten the top of the soil.
Light feeders, may not need fertilizer for three years after potting or at all if you repot every two years.
Fertilize at the beginning of the growth period and just before flowering (early spring/early fall).
Low nitrogen water soluble, 1/2 or less recommended concentration.
Healthy plants with enough light have leaves just above soil level.
Direct light in northern regions is necessary.
Minimum 4 hours but more will increase growth rates.
No direct light in areas further south that experience high intensities and durations (comparable to Arizona).
Few, but mealybugs may be an issue (especially if warm and humid).
Hopefully that information was helpful. Again, if you see anything that maybe shouldn't be there, isn't clear or that you think I should add, just let me know. I've posted these links before but they have a lot of useful information (some of which I have used here) so I'll mention them again.
Lithops - Cultivation