Understanding Bagua
Early Heaven Bagua 
The bagua is the foundation of any fengshui , classical or pop or red hat or black hat. To understand fengshui is to understand the bagua. A gua consists of a block of three lines - broken or unbroken, if broken it is a yin line and unbroken it is a yang line.
Both are equally important. The various combinations or permutation of these three lines give rise to the eight guas called the bagua. It is these combinations and their placement that gives the bagua its power to act and direct and repel. The three lines also represent the Trinity of Heaven, earth and man. There are two types of bagua - early heaven and later heaven. Early heaven bagua is governed by timelessness, immortality, perfection, no birth, no death and no decay. Later heaven is governed by cycles, change and relates to yang fengshui and is the bagua we normally use to do fengshui audit today. Early heaven bagua is used in burial fengshui and if used in yang fengshui, it is to compromise the incompatibility of the gua numbers of inhabitants living in the same house.
8 guas:-
Chien - represents male authority, governs head and lungs, sits in north west and is ruled by the number 6 and has the element of metal.
Kun - represents female authority, governs stomach. sits in south west and is ruled by the number 2 and has the element of earth.
Chen - represents middle son, governs the liver and hair, sits in the east and is ruled by the number 3 and has the element of wood.
Xun- represents middle daughter, governs the limbs, sits in the south east and is ruled by the number 4 and has the element of wood.
Ken - represents youngest son, governs the hands, sits in the north east and is ruled by the number 8 and has the element of earth.
Tui - represents youngest daughter, governs the mouth, sits in the wast and is ruled by the number 7 and has the element of metal.
Kan - represents middle son, governs the kidneys and blood, sits in the north and is ruled by the number 1 and has the element of water.
Li - represents middle daughter, governs the heart and eyes, sits in the south and is ruled by the number 9 and has the element of fire.
You can also use the above to screen and to select a house to buy or to rent and to balance elemental disturbances you may now experiencing. For example if you have a t-junction road coming into your house from the south and you now know the principles of the south. T-junction represents killing energy so this will affect the middle daughter of the house or middle age females living in the house. If there are no such females in the house then it may affect the health of the eyes or the heart of the occupants. So if you are living in the house the cure would be to use water element to counteract the fire coming from the south. e.g. a fountain.