Lithops are wonderful plants that I think everyone should try to grow at least once. Many people will avoid growing them because they are difficult but if you know what they need they are one of the easiest plants out there. They are small plants so you can grow a nice collection on a small window ledge (as long as you get strong light).
To grow Lithops successfully you really only need to know 2 things.
1. Bright light - They love, love, love the sun. if they are lacking in the light department they will stretch and not look as nice.
2. NO WATER!! - well I exaggerate a little... But seriously no water over the winter and spring. I will say that 90% of lithop death in the home is due to someone feeling sorry for the little gems and giving in to the stone dry soil with a good watering.
I have posted some videos of my Lithops on YouTube and i will share them with you. I also have killed my fair share of Lithops... and I am just sharing my experience with you :)
Once you get the hang of growing Lithops it would be fun to get creative with your collection. why not make a living rock garden. how Zen would that be :) I find that it's a little more difficult to grow them in groups only because each plant might be at a different stage of growth.. meaning some might need watering and others not... so that's why I say try a mix planting after you get the hang of one on one growing :)
When transplanting or dividing Lithops make sure to not water them for a while... let them callus any wounds on the roots. Even if there are no roots on the plant it still will likely survive if you don't water it for a month or two.
Soon i will have a Blog entry on Growing Lithops from seed. I'm still playing with that but can't wait to share that adventure with you.
Have fun with it. These plants are amazing. Please let me know if you have any questions, comments or concerns. I am no expert but I would love to help you out if I can :)