From http://www.mdani.demon.co.uk/para/iching1.htm

1. Compose your Question
You begin your consultation by formulating a question. You can ask questions about situations in your own life, or about general situations, such as social, business or political events. You should NOT use the I Ching to ask questions on behalf of another person (although, of course, you can consult the oracle about your own relationship with other individuals).

You should spend some time reflecting on your thoughts and feelings about the situation, before formulating your question. Your question should be clear and precise. Do not assume that the oracle knows what you have in mind. Vague or ambiguous questions will get confusing answers. Do not ask whether specific events will occur (this is not fortune telling!), but focus instead on how things will affect you, on how you should behave in the situation, or on what aspects are operating in events. If you do not get a clear answer to your initial question, then more focussed follow-up questions are advised.

Most importantly, you should approach the I Ching with an attitude of openness, honesty and respect. The oracle has a very definite "personality" of its own, as you will soon learn. If you use the I Ching in a trivial or inappropriate way, you are not only wasting your own time but you risk being wound up or perhaps reprimanded by the responses you receive from the oracle.

How can I learn from the events of today?
Should I consider psychotherapy at this time?
How should I respond to John's invitation to spend the weekend with him?
How will moving to Chicago affect the family?
What are the prospects for my business partnership with Susan?
What is the best way to ask for a raise in my salary?
How can I improve my relationship with my daughter?
How will the planned surgery affect the way I feel about myself?
How is my spiritual development progressing?
How will political negotiations proceed at the forthcoming Camp David summit?

Hey, this is cool! (not a question)
What's up? (unfocussed, ambiguous and supercilious)
How do I improve things? (imprecise)
Who will win the Mexican Grand Prix? (specific prediction)
What should Mary do about her cheating husband? (this is Mary's question, not yours!)

Traditionally, the I Ching hexagrams are constructed by throwing three coins six times, or by following a complicated procedure that uses 50 yarrow sticks. Both methods are based on the assumption that the "random" fall of the coins or division of the sticks in some way reflects the nature of the inquiry. From the perspective of Jungian Psychology this happens synchronistically, (i.e., due to meaningful coincidence, or the operation of an acausal connecting principle known as synchronicity ) .

The coin oracle is the most commonly used, simply because it is quicker. However, the yarrow stick procedure is the more ancient, and is considered by many people to be more authentic. This is because the mathematical odds involved using the yarrow stick procedure are more consistent with the underlying theory of the I Ching.

With the advent of personal computers, software is increasingly used to simulate the traditional methods of casting hexagrams. This has the advantage of convenience, speed and computational accuracy. It may seem odd to use a computer for this purpose, but in principle there is every reason to suppose that synchronicity operates just as readily in this way. Many people's experience (including my own) is that computerised I Ching readings are just as valid and useful as those made using more traditional methods.

To cast the oracle, you first choose either the coin or yarrow stick methods. Unless you have become accustomed to using the coin oracle, and are most comfortable with this, I recommend that you choose the yarrow stick simulation.

Next, type in your question. You can also select the general area of your inquiry.

Hold your question clearly in your mind. When you feel the time is right, click the GO button to cast the hexagram. You may have your own way of getting into the right frame of mind for the divination. Some people like to use a simple meditation or some kind of personal ritual.

The I Ching Oracle gives 64 x 64 = 4096 possible readings.

A reading is generally made up of three main parts:
The First Hexagram (+ shadow features)
The Changing Lines
The Second Hexagram (+ shadow features)

The reading for the first hexagram indicates the basic current situation and advice. Additionally, the nuclear hexagram is used to give an indication of the contrary or shadow elements in the situation (i.e., things to avoid at this time).

In many readings (but not all), the initial hexagram changes into a second hexagram, due to the fact that one or more of the lines change from a Yang to a Yin (or vice versa). If this is the case, you next interpret the reading for the changing lines. These give an indication of the dynamic or changing features in the situation. The changing lines should be read in sequence (the text is read from top to bottom, even though the corresponding lines appear from bottom to top). If a line appears to contradict the advice in the basic reading, the changing line takes priority. When the various lines give different advice, these may refer to a sequence of events, or may indicate genuine tensions in the dynamics of the situation. If a line is marked with an asterisk (*), this shows a ruling line. It should be given particular emphasis.

Finally, you read the second hexagram. This indicates the way in which the situation may develop, or advice for the future. Additionally the second nuclear hexagram is used to suggest the contrary or shadow elements in the possible future situation (i.e., things to avoid in the future).

If the reading has no changing lines, you will have no second hexagram. This implies a situation that is fixed or static.

In order to get full value from the reading, you should play with the ideas that are suggested, relating them to your situation and considering various interpretations. This should be done lightly and intuitively, allowing your unconscious mind to suggest connections, associations and possible meanings