In design there are five basic principles you should follow in developing your living or working space:

Space - is the first element and most important.  You should think about how much do I have to work with?

Lines - can have a huge effect on the overall feel of the room. Vertical lines add height and prestige. Horizontal lines create an intimate, relaxing and informal atmosphere.

Form - is a shape or combination of shapes of the elements in a room.  For example, if you have square windows, window treatments can lengthen them and give them a taller rectangular look.

Color - is the most significant mood determining element in a room.  It intensifies as you increase the area of coverage.

Texture - is great for adding interest to a room.