Most of the info in this comes from the book "Lithomancy: Divination and Spellcraft with Stones, Crystals, and Coins" By Rev. Jon Saint Germain, who is the worlds leading expert on crystals and stones. His books are really well researched and i suggest checking them out
Lithomancy is divination by casting stones.
You can see lithomancy all through out history.
For example:
In Germania the ancient Germanics would take a branch from a fruit-bearing tree and they would cat the branch into small pieces. Then they would carve distinctive symbols on each piece and they would scatter the pieces at random on a white cloth. Than they consult the priest (if done publicly)or the father of the family (if done privately) and the priest or father would invoke the gods and pick up 3 pieces total, one at a time.Then they would interpret based on the symbols on the 3 pieces.
It also appears in the bible a few time (lots of people say the bible bans divination, but then the bible uses divination like lithomancy and they you can't tell if you can do divination or not. The bible contradicts itself a lot. That's why i'm not christian. it's too confusing, plus i don't believe in their god and the christian community is toxic af). Anyways, it appears in the Book of Exodus 28:30 when Moses explains to his brother who is a priest why he must start carrying tones in his pockets. It's also found in the Book of Proverbs 18:18 when it says that one has to cast lots (stones) to settle a dispute. Or in the Book of Jonah when the crew of a ship is in the middle of a terrible storm because one of them angered God so they used lithomancy to find out which one went against God
A really simple lithomancy set you could have is one brown stone, one black stone, and one white stone. The brown stone represents you, the black stone represents no, dark energies, negativity, femininity, the night, and the moon, the white stone represents yes, light energies, positivity, masculinity, the day, and the sun. You take all these stone on your hand and focus on your question or intention, than you cast them onto a flat surface and interpret it depending on which color stone lands closest to the brown one (you). You can also interpret which direction they landed in (North, South, East, or West)
East: Morning, springtime, youth, welcome or new experiences
South: Noon, summer, adulthood, stable or recurrent experiences
West: Sunset, autumn, old age, receding or ending experiences
North: Midnight, winter, death, negative or painful experiences
This is the most basic thing you can do with lithomancy. But it can get far more complex as you start adding more stones, like a money stone or a love stone etc. It is suggested that as you're collection grows bigger you should draw symbols on each stone so that you remember what it means. Also you should probably start using color correspondences for the stones.
When casting stones, traditionally you take every single stone in your collection in your hands and you throw them on a surface and interpret where they land, however as your collection gets bigger it will be harder and harder to do that. That's why there is another form of casting called sortilege. Sortilege is basically putting all your stones in a bag or bowl or some other container and you reach your hand in and pull out as many or as little stones as you feel like and you cast those onto a surface and interpret them as you normally would. You can also use numerology for this if you feel like.
Crystals and stones have memory so remember to cleanse the stones before you use them next to reset that memory. Also charging them would also be a god idea. Jon Saint Germain recommends you charge your crystals or stones out in the sun for a day (provided they're safe to be out in the sun) and out in the moon for a night. And then you need to "train" your stones. Basically you need to bond with them, like how one would bond with tarot cards so that they work best for you. So that they learn to work with you. Lots of people sleep with them under their pillows, or carries the stones around with them on a day to day basis to "train" their stones.
More info on casting stones methods (Yes/No questions):
One Stone: Heads or Tails
Although this is more commonly used with coins than stones you can also do it with stones. Remember earlier when i mentioned drawing symbols on your stones? Well you only need to draw the symbol on one side of the stone (this is important for more than just the heads or tails casting method. Although some people prefer having stones that are naturally marked on one side instead of drawing on them). Designate one side as yes and the other side as no. Whichever side lands upright will be your answer
Two Stones: Casting Lots
In its simplest form all casting lots is putting 2 stones in a container (one for yes and the other for no) and reaching into the container and whichever you pull out is your answer
Three Stones: Your Personal Casting
I already mentioned this earlier but i will but it here anyways. You have is one brown stone, one black stone, and one white stone. The brown stone represents you, the black stone represents no, the white stone represents yes. You take all these stone on your hand and focus on your question or intention, than you cast them onto a flat surface and interpret it depending on which color stone lands closest to the brown one.
There are many more techniques you could use once you start adding more stones to your collection, all i put here is what you can do with the basic 3 stones that you use to start with. Once you get good at these you can start adding more stones to your collection
Casting on a marked surface
I bet you've seen all those altar cloths with different designs and different sections separated out. A lot of these cloths are used for divination that involves casting objects, like runes or bone throwing or lithomancy. These help a lot when you're trying to get lots of details (you can make one yourself of a piece of paper. It doesn't need to be a cloth). You can separate each section any way you want. Here are some examples from my book
This is all i'm probably going to cover for now (I might make a future chapter with more information), however i definitely recommend reading "Lithomancy: Divination and Spellcraft with Stones, Crystals, and Coins" By Rev. Jon Saint Germain for more information
You can also get some more information on lithomancy here https://themanicnami.tumblr.com/post/150142807211/namis-guide-to-crystal-divinationcrystal (this post is on using specifically crystals in your lithomancy and it also only has basics. The book by Rev Jon Saint Germain has far more info in it)