I can only help with part of one question:
Originally Posted by farhan
Secondly , what is hexagram & trigram, are they also asociated with astrology .
There is a Chinese divination system known as the I-Ching (or Yi King.) It's based on a binary system at its core -- the broken line, and the unbroken line. Broken lines are Yin, and unbroken lines are Yang.
A set of three lines is a trigram (tri being three) and with the possible combinations of broken and unbroken lines there are eight trigrams.
Two trigrams are combined to make a hexagram (hex being six.) With all the possible combinations of upper and lower trigrams, there are sixty four possible hexagrams.
There are methods using tossing yarrow sticks or alternatively using coins to determine the sequence of broken and unbroken lines to make up a hexagram. The hexagram is interpreted by looking it up in a book of meanings. My favourite set of interpretations is in the book "I Ching" by Sam Reifler.
That's the bare basics anyways -- there is a lot more complexity to it which you can read about in any book about the topic.
I don't know much at all about Chinese astrology though so I don't know how the I Ching hexagrams work into the whole thing.
There are some free online divination systems including I Ching readings at http://www.facade.com/