Space is the first element to think about when decorating a room. How much do you have to work with? Look at the area surrounding the window, as well as the room it's in. To visually expand, keep the colour contrast between the wall and window low. To make a room feel cozier, create a high contrast.

Lines can have a huge effect on the overall feel of a room. Vertical lines add height and dignity. Horizontal lines suggest relaxation and informality.

Form is a shape or combination of shapes of the elements in a room. You can easily alter or improve the appeal of existing shapes, If you have square windows, window treatments can lengthen them and give them a taller, more rectangular look.

Colour is the most important mood-determining element in a room. It intensifies as you increase the area of coverage. A good rule of thumb is a allow your main colour to occupy about 75 percent of a room (including floor and wall space), your second colour 15 to 20 percent, and your accent colour about 10 percent. Many people choose a neutral hue for their main colour, since bright hes can be overwhelming if they're used too liberally.

Texture is great for adding interest to a room, so feel free to add some here and there. The word on the street? Dramatic contrasts are in. Even corduroy and silk are an acceptable pair these days.

(from HunterDouglas Window Fashions)