Here are some quickies to keep in mind when deciding over colors.
1. If you are using many colors in one single room, make sure you use a color at least three times in the same room. You could use shades and tints of that color. For e.g. your curtains, pillows and tablecloth can be of the same color. This gives a look of harmony and help avoid the 'too much' and 'confused' look.
2. For filling space, use warm colors like reds, yellows and oranges. They tend to grab the eye and fill the space and are soothing and warm.
3. For giving an illusion of more and open space, use cool colors like blues, greens and violets.
4. For a serene and comforting look, use pale pinks. The closer pink gets to red, the more energetic it becomes.
5. Use vertical stripes on walls and curtains for an illusion of height.
6. Light colored walls and ceilings make the room look larger and more spacious.
7. Try to avoid contradicting colors and themes. If you want your room to look larger and need to use cool colors to achieve it, choose a theme which goes with cool colors.
8. If same-colored sofa, carpet and other upholstery give a monotonous look, use colorful cushions and wall-hangings to break the monotony.