Vaastu Shastra is voluminous and scattered ancient Indian literature dealing with knowledge of architecture, iconography and art relating to structures and buildings. It comprises of independent works which are classified under the general heading of Vaastu Shastra.  It is an ancient practice to construct buildings in harmony with natural forces for well being of humanity as a whole. It is rich Hindu philosophy which is given in number of ancient works including Vedas. Vedas or sacred lore are considered to have reached us directly in the form of hymns or mantras.
The word Vaastu has been derived from ‘VASTOSHPATI’ used in ‘Rig Veda’ and is meant to provide protection, happiness and prosperity in this life as well as after death. Rig Veda in part 7, chapter 54/1 says.
Vaastu Shastra is a Sanskrit (the most ancient and original language of (Hindus) word. Vaastu mean dwelling and Shastra mean treatise or book. Hence Vaastu Shastra mean book on dwelling. Do’s and don’t, of Vaastu Shastra are explained logically and in a scientific way in ancient literature. So we can also call it a science of dwelling.
Vaastu Shastra is a result oriented science and gives definite and immediate results if applied properly. It tells about proportion and details of building elongation, slopes, water tanks, kitchen, bed rooms, stairs, heights of roofs, entrances, doors, windows, walls etc
We are surrounded by energy fields. In an open ground, they operate freely but when a structure is built, the energy fields are affected and have to be restored. When this is achieved in a proper manner, a harmonious flow of energy permeates the building. This has positive effect on the people occupying it and a bearing on health and prosperity.
Vaastu also considers the five elements as forces which originate from a single source but with different characteristics. They are within us and surround us. We are born out of them, we grow with them and we return to them. These forces adhere to strict physical laws. Thus every one of us can make use of them for our benefit. Vaastu has no ritualistic side. It is universal in approach and is not based on any particular religious thought.
We at IVAC believe that every human being is entitled to a happy life and this can be attained by living in a structure which is in harmony with the cosmic forces. We offer guidance and training on the proper design and layout of structures - also advise any necessary corrections relating to health.
First and foremost Vaastu Sastra is not a religion but a science. The philosophy and concept of Vaastu Sastra has more to do with complex mathematical calculations along with the energy lines of the earth.
Faith is not a prerequisite to success. Instead effective creation of energy and positive vibration, flow of balance and harmony are required.

The Principles
Vaastu Sastra is based on precepts laid down thousands of years ago in the Indian classics like the Puranas and Vedas. It concerns the order - the harmony of heaven and earth and ways in which we as humans can keep the balance of humans intact.
Few examples  (just skimming over and touching the basic principles of  Vaastu Sastra - only to make a person aware of what exactly it pertains to)  are listed below.
While buying a site :
1. Select a site where the land is fertile and not dry and rocky.
2. Avoid water logged land or a site at the end of a road.
3. Avoid land too close to graveyards, cemeteries,
crematoria or hospitals.
Building a house :
1.   Regular shapes in houses with squares and rectangles are far superior to angular houses with protrusions or L-shaped and V-shaped structures.
2. Avoid U-shaped houses. People in these would face a great deal of hardship and unhappiness.
3. Avoid triangular shaped houses that have too many corners. The angles are not conducive in attracting positive energy.
Doors :
1. The main door of a house should never directly face a church, temple or cemetery.
2. The door formula states that the number of doors inside a house should be even  in  numbers and not  odd numbers. They should not end in zero. There should be an odd number of doors in line.
3. When doors face each other, make sure they face each other directly.
Staircases :
1. A staircase should never begin in front of the main door nor end directly in front of a upstairs door.
2. Staircases should ideally be curved gently rather than straight.
3. Spiral staircases are not auspicious.
Industries :
1. The land for an industry as advised by our Ancient  Masters should not be where the air is stale, where plants cannot flourish, where soil is dry and lifeless, where surroundings are harsh and threatening and where shapes of hills are sharp and pointed.
2. The main shed or building should be constructed in the south west sector of the entire land leaving more space in the north and east direction and less space in the south west direction.
3. The overhead water tank should be located in the north east sector.
4. The raw material should be stored in the western area and the finished goods in the north west sector.
Just a few of the basic principles of Vaastu Sastra have be touched on. There is a lot more to be studied and understood in detail for the best results. This may be further discussed if required. Do remember that Vaastu Sastra is not magic. It does not have instant results. It is necessary to be patient and allow time for the positive energy and currents from the cosmos to enter the home or office and industry and await harmony and balance.
Vaastu should be looked upon as a science and ancient wisdom that has survived through
centuries. 
Vaastu is the means of capturing the positive bountiful power of the three elements: The Earth, The Water , The Fire, (the Sun) in a proper and proportional manner, along with the Air, in our House, making it the Adobe for all of them, for peace and property of the Human Beings; and the World (Vishwam) at large.

Man builds the house for his home. Nature consists of five elements SAFEW viz., Sky (space), Air (Atmosphere), Fire , Earth and Water.

How to select a site for the Construction of a House
It is always better to consult an expert on Vaastu before selecting a site for the construction of a house to reap the best advantages out of the proposed house. It is always advisable to go in for a site which is either a square or a rectangle in shape. A spacious site makes the inhabitant rich provided that it is a perfect square or a rectangle. It should not be contracted in any direction.

It is advisable to acquire an additional site located towards the east or north of the existing house. Any amount of investment for acquiring a plot situated towards the northeastern part of the existing plot, is not a bad investment. The topography of the plot reflects on the life of the inhabitant. Slope towards north or east showers bountiful blessings on the inhabitant. Similarly elevation in land in the western and in southern part so the site makes the life a prosperous one. People residing in such sites do achieve greater things. It is always better to select a spacious plot so as to facilitate construction of as many rooms as one can do.

If the plot is situated in conformity with the compass the house constructed, thereon also should be set as per compass. However any deliberate attempt to adjust the house as per compass, leads to directional dead-lock, because it results in extension of southeast, southwest, northeast and northwest. Hence if a site does not fall in line with compass, the house can be constructed consistent with the adjoining road and the neighboring houses. That is why a site possessing a straight and parallel road according to the compass must be preferred. However, a plot lying by the side of a road leading on increasing northeast, is said to lead the destiny of the occupant for a brighter tomorrow. The prosperity and progress in the life of the resident of a plot is directly proportional to the elevation of the western and southern parts of the plot.

One should never select a triangular site. Just as it is difficult to change the properties of the soil, it is also difficult to change the properties of a site or a plot as one can't change a silk into cotton or vice versa. For instance, the existence of a high hillock in north or east, or a location of a tank or a river in west or south cannot be rectified. Similarly, one cannot change the direction of a road, which cuts across the northeastern tip of a plot. Further the existence of a small plot in between two bigger plots, makes the inhabitant lead a suffocating life just as a calf gets trampled between two fighting bulls.

Never select a site which protrudes towards northwest, southwest or southeast. If the vacant portion is a site is more towards the south or west than towards north or east, it is advisable to separate the excess portion by means of a small wall or fence and a shed may be constructed in it, or the same may be disposed off.

If the road leading from your plot takes you towards east, north or northeast, it is said to be very auspicious. If that road leads you towards southeast or southwest it brings misfortunes to you.

Never think of procuring a site which slopes towards southwest. Ensure that the rain water or sewage water of neighboring plots does not flow into your site from eastern or northeastern direction. People living in such houses cannot have even normal peaceful life.

It is well - known fact that even a single step taken in haste by the pawn will end the play with helpless shah and utter flap. In the same way a small error crept in the selection of the site or the construction of a house will lead to many troubles in future. So also the contraction or projection of directions, if not considered first, will end in chaos.

In chess the looser will be a single person. But in Vaastu, a game of directions, if the error is not checked and rectified in the beginning itself; it will bounce troubles on the whole' household. Hence one should be cautious enough in selecting a site as per Vaastu to avoid future misfortune, lest he will become "a Burnt Child".
Vaastu Tips

 (1) Your head should be towards the east or south while sleeping.

 (2) There should be no noise while opening the doors and windows especially the entrance door.

 (3) Shoes and slippers should not be scattered all over the house, as this leads to feud.

 (4) Don’t keep dirty clothes with the washed clothes.

 (5) Don’t a keep jug or jar of water near the telephone. The electric rays produced from telephone leave bad effect on the water.

 (6) Keep cash and jewellry in the safe or locker which opens in the north.

 (7) Your face should be towards the east while cooking food. The cupboard containing food articles should be towards your right.

 (8) Place vegetables in a dish after cutting them. If they are kept on floor their nourishing Substance will be adsorbed by the floor.

  (9) Change the bed-sheets during day time.

 (10) Comb and other beauty aids should be kept neatly at the right place.

 (11) There should be a separate towel for every member of the family and for guests.

 (12) Change the night suit before 8 o’clock in the morning.

 (13) It is very auspicious to view rising sun after taking bath in the morning.