Scientifically one can break interior design down into a few design principles. But be aware because these are not rules, rather see the principles as fundamental underpinnings for a feeling, flair or intuition to interior design.

Principle 1: UNITY

When doing interior design it is necessary to think of the house as a totality; a series of spaces linked together by halls and stairways. It is therefore appropriate that a common style and theme runs throughout. This is not to say that all interior design elements should be the same but they should work together and complement each other to strengthen the whole composition. A way to create this theme or storyline is with the well considered use of color.

Principle 2: FOCAL POINT

Interior design’s biggest enemy is boredom. A well-designed room always has, depending on the size of it, one or more focal points. A focal point must be dominant to draw attention and interesting enough to encourage the viewer to look further. A focal point thus must have a lasting impression but must also be an integral part of the decoration linked through scale, style, color or theme.

Principle 3:BALANCE

Balance can be described as the equal distribution of visual weight in a room.
The simplest, and most formal type of balance is symmetrical balance, where the same objects are repeated in the same positions on either side of a vertical axis, such as one would find in old fashioned state or gala rooms.

Asymmetrical balance is more appropriate in design today. Balance is achieved with some dissimilar objects that have equal visual weight or eye attraction. Asymmetrical balance is more casual and less contrived in feeling, but more difficult to achieve.

Principle 4: PROPORTION

Proportion refers to the relative size measured against other elements or against some mental norm or standard. This design principle is of extreme importance when decorating a room.

Principle 5: RHYTHM

In musical terms we would describe rhythm as the beat or pulse of the music. In interior design, rhythm is all about visual pattern repetition. Visual rhythm is based on movement. As in music, rhythm in design can also be staccato – abrupt and dynamic or legato – connecting and flowing.

Principle 6: COLOR

Color is an element that tends to inspire emotion in people because color has an influence on the value of life above and beyond other considerations. Colors therefore have a definite impact on the atmosphere that you want to create when doing interior design.

Principle 7: DETAILS

Another important element of interior design where it is necessary to take infinite pains is details. Everything from the trimming on the lamp shade, the color of the piping on the scatter cushion, to the light switches and cupboard handles need attention. Unlike color people find details boring. As a result it gets neglected and skimmed over or generally left out.
As color expresses the whole spirit and life of a scheme; details are just as an important underpinning of interior design. Details should not be obvious but they should be right, enhancing the overall feel of a room.

These principles of interior design should guide you when you start either doing it yourself, or discussing your ideas with your interior designer.