I have met very few psychics or others who use casting stones, but there are a few of us who do.  There are
many different methods for using gemstones and crystals as an oracle; it depends on what feels right for
you.

Casting stones are simply a group of crystals, gemstones or the like which you "throw" onto a surface and
then read.  You can sometimes buy casting stones as a kit, complete with a drawstring pouch in which to
store them.  Or you can select your own stones one by one as it feels right to you.

The best stones to use in casting stones should be relatively small, but not tiny (very small stones are
frequently lost, and very large stones -- well, imagine tossing down a dozen large quartz pieces at once, and
you'll get the picture).  They should also be relatively flat, or with a flat side.

You can choose your stones by virtue of their magical associations, color, name, or feel.  For instance, Tiger
Eye is usually included in a set of casting stones.  Tiger Eye is a yellow/orange color, and thus has
associations with warmth, light, heat, the Sun, clarity, daytime, etc.  It also could be associated with cats,
vision, and the night, depending on the question and what you choose to associate it with, or what your
subconscious tells you it means.  Amethyst is associated with spirituality and psychic vision, as are all
purple-colored stones.  There are a number of decent books out there on the associations of stones, so
getting one of those is a must if you want to do stone casting.

You can cast your stones in various ways.  One excellent reader I went to (thanks, T.A.!) had a lovely
handmade cloth onto which he threw the stones and interpreted them based on what area they fell in, which
stones fell next to which other stones, taking into account colors and associations.  If I'm recalling correctly,
he had a circle design on his cloth, divided into four areas representing different things.  I believe his
reading methods were based on the four directions and their associations:  East (air), South (fire), West
(water) and North (earth).  Air connects with the mind (as does the color yellow), Fire connects with action
and energy (as do red colored stones), Water is the intuitive and emotional (blue and purple colored
stones), and Earth is the practical and manifest (earth tones).

As an astrologer, I invented my own method of casting the stones, not being satisfied with the directions
included in the kit I purchased.  I use a blank astrological chart form (the natural chart, with Aries on the
Ascendant), and cast the stones onto the chart form.  Each stone has an association with a planetary
energy.  My set contains 13 stones, and there are 10 planets/Lights, so I use the clear quartz to represent
the "heart of the matter", and different stones for the Gemini Mercury and the Virgo Mercury (since they are
different energies), and two for the Taurus Venus and Libra Venus (ditto).  If the stones fall close to the
center of the chart, I interpret them in the past; on the edge of the chart, present; and outside the actual
chart but still on the form, future.  The houses into which they fall tell me the areas of life involved.  It's
almost like a stone transiting chart for the client.

Although my method involves a fair amount of conscious interpretation, I have found that the stones are
extremely intuitive, and will open up your intuitive/psychic mind very well.
 

from:
http://www.spiritrealm.com/summer/divination.htm
 

Find, choose, purchase two stones that are similar in size.  One should be very light colored, the other one should be very dark colored.  While holding the stones, think of the question, then shake them in your hand like dice and then toss them to the floor in front of you.   If the light colored stone lands closer to you the answer is Yes.  If the dark colored stone lands closer to you the answer is NO.  If they both land equally distant than you must rephrase the question and try again.

from:
http://members.xoom.com/anania1/quickdiv_.html
 

Buttons (or Stones)
Keep a little pouch with colored buttons in it.  You will need, black, white, red, brown and a green one.   Concentrate on your questions and then draw a button.

Black means NO.
White means YES.
Red means that Strong Emotion is driving you.
Brown means that the issue is cloudy, you may not know all the  facts.
Green means that their is allot of potential in the situation.

[Ma'at's note:  You could use colored stones, like obsidian, moonstone, jasper, brown agate, and malachite for this divination.]

from:
http://members.xoom.com/anania1/quickdiv_.html

The Casting of Lots

'Lots' made of bone, shell or wood made up most tribal divination systems. These systems had a finite number of lots; for
 instance, four to twenty-four pieces. Four lots could possibly give you sixteen combinations, with each combination relating to a specific message. Each specific pattern may have its own sponsoring divinity, future meaning, present advice and spiritual plan.

A second throw could also include finite numbers of messages. The more lots, the more patterns, the more throws, the more
extensive the answers. The current rune system with twenty-four disks, each with its own design (depending on the system you
use), began with this lot system.
 

Yes/No Stones

This particular technique is the easiest to master; however, you must trust your
 intuition and not second-guess the issue, as well as be sure to ask the proper question
(wording it in a clear and concise manner).
 

Make your own lots

Choose three items of the same size (three small stones, three small pieces of wood,
etc.). Paint one side solid or mark with a design. Leave the other side of the object
blank. The painted side will be a positive answer while the blank side will be negative.
Hold the objects in your hands and ask your question in a manner which can be
answered with a 'yes' or 'no' answer. This isn't always as easy as it sounds, but once you
get used to wording your questions, your answers will be clearer.

Close your eyes and ask the Divine to aid you in this divination. Ask your question, then
Throw the objects. Follow the key below:

--Three 'yes' objects= Yes
--Three 'no' objects= No
--Two 'yes' objects and one 'no' object= A struggle, but the conclusion will be "Yes."  Throw again to determine the source of the struggle.
--Two 'no' objects and one 'yes' object= Maybe, but the outcome has not been determined due to decisions that you, or someone else, will make. Throw again to learn more details.

You may wish to meditate first and burn a candle while casting the yes/no lots. Try not to do your divination if you are in a hurry, as you won't be able to concentrate properly. And keep a record of your answers.

If you would like to expand your lots to include a timing mechanism, paint a fourth stone with a full moon on one side and a new moon on the other. You can throw this with the other three lots, or seperately.

from:
http://www.users.drak.net/halloween/divination.html