All studies and sciences are based on some principles. Principles used in vastu are as follows:

PLOT SHAPES & DIRECTION

First of all the direction and shape of the plot has to be considered well. A construction on quadrangular, rectangular or square plot is beneficial and good from all aspects. Big plot fetches prosperity, but it should not be having cleavage or cracks any where. Triangular shaped plot should not be selected for constructing a building. It is inauspicious.
A small narrow plot in between two big plots is also not good, because owner of the building on such plot always remains in troubles. If the length of the plot in east-west direction is more than in north-south direction, it is better. If there is more open vacant space in south than in north, it will lead to destruction and downfall whether it is in the house or a industry, or in a temple or a hut.

PLACEMENT OF ARTICLES
It is auspicious if there is more open space in the east than in the west; and more open space in the north or than in the south. All the heavy and permanent items should be placed in the south-west corner of the building or plot. While sleeping head, should be kept in the east or south. Never sleep with feet towards should or east.

Water tanks on the roof in the south-west direction are auspicious. These should never be placed in the north-east (esshanya) corner. Pooja room is always best in the north-east corner or near it. Kitchen is always auspicious and best in the south-east (Agency) corner or adjacent to it. Open space should be kept all around the building. Building should be constructed such that it is higher in the south-west and lower in the north-east. Walls should be also be made in this manner.

Underground water tank (for storage water) well, hand-pump, boring etc. Should be built in unit in north-east direction only. Height of these water bodies forth should never be above the plinth level of the main Building. As far as possible there should be only one main door of the house, which should be adorned with auspicious symbols. All the doors and windows should be of the same height their upper edges being in the same straight line. There should not be a door above a door. This principle does not apply multi-story buildings. Height of the door on upper floor should be kept less than that on the lower floor.