Vastu Shastra is a very old Indian science of Architecture developed by ancient Indian sages and rishis for the welfare of humanity. Vastu Shastra provides principles and rules based on which the structure of a home or a temple is built. The same holds true to the planning of towns and colonies. Application of the tenets of Vastu can be seen in the ancient cities of Mohanjodaro and Harappa.

Vastu is the study of the impact of the Sun's rays on the earth. According to Vastu, there are 5 basic elements in the world (Panch Mahabhutas). They are the Earth, Water, Air, Fire (Heat & Light) and Sky (Cosmic). Vastu is a science of balancing these elements in the proper proportions for prosperity and harmony.
The principles of vastu are based on directions, which are permanent. Ventilation plays a very important role in Vastu, good cross-ventilation therefore is necessary. Since vastu is based on the properties of the earth and the sun, it is surely universal. Nationality, religion, caste etc. have nothing to do with the science of vastu, it is equal for one and all. 
In modern times it is not feasible to build big houses having large number of rooms as mentioned in Vastu Shastra. Houses are built on small plots which can not accommodate many rooms. Therefore it is advised to construct the house in accordance with the principles of Vastu, in abridged form having rooms as per necessity and convenience.

Bath Room: - Proper place for bath-room has been suggested in the east direction. The mild rays of the morning sun are beneficial for health. These rays can be received by the body while bathing, therefore bath room in the east is good.

Kitchen: - South-east corner is the place of the god of fire (Agni Dev), therefore, the kitchen wherein fire has an important role, must be built in this corner. The Kitchen should never be built in the north-east, South-west or in the centre of north, south or west side.

Bed Room: - The Master bedroom should be in the south- south-west direction. Bed-rooms for unmarried children can be built on the east side and for unmarried youths or for guests, the bed room in north-west is good.

Dining Room:-Best place for the dining room is in the west. Nowadays, the dining room is adjusted with the kitchen or drawing room. In that case this room may be used for other purposes. The Dining table should be arranged in the South-west or north-west portion of the room. Water arrangement should be in the north-east corner and fridge etc. (electrical appliances, if any) should be kept in south-east corner. Persons should face towards the east or north while taking meals.

Pooja Room: - The North-east corner is governed by Eeshwar (God); Hence the Pooja room should be built in this corner. This corner should not be used for the bedroom, kitchen or any other room, and no other articles should be placed in the pooja room. There should not be any toilet or kitchen above, below or adjacent to the pooja room.

Toilet: - The place between south and south west is suggested for the toilet. It can also be built in the north-west.

Study Room: - The best place for the study room is between the west and south-west. The person should sit facing the north or east while studying. The study table should not be placed touching the walls. The Book-shelf should be placed along the north-east corner only.

A few more tips on Vastu:

• Racks or almirahs should be in south & west direction in all the rooms.
• Doors of each room should be facing east.
• Never fix a mirror on south and west wall if possible.
• Toilets & bathrooms should be in south-east or north-west portion.
• Bedrooms should be in south and west.
• Master bed room should be in south-west.
• While sleeping head should be in south or west but never in north
• Pooja room should be in north east. All photos or idols should be facing east or west only.
• Drainage pipes should be in north or east portion of the plot or house.
• Toilet seat (W.C.) should be north-south only. It should not be east-west.
• Septic tank should be in central-east towards south or central-north towards west.
• Over-head water tank should be in South-West. And if it is in north-west, then any other higher structure to be made in south-west. It should not touch the slab it should be above and on four pillars.
• Face east while cooking, west will be allowed if there is no alternative, but never face south while cooking.
• Ventilation plays a very important role in Vastu, good cross-ventilation therefore is necessary.
• TV, Radio or any other such device for entertainment should be placed near the southwest corner.
• No two doors are opposite each other.
• Guestroom or drawing room should be in the north or west direction.