First of all there are the questions about what kind of effect you want to achieve and what kind of impression you hope to make. Are you looking for something peaceful and harmonious or do you want to create a bold and bright impact? Do you want to fit in into a conservative, historical neighborhood, or do you live in an area where you have full scope to explore your color eccentricities? Are you going to live in the house forever or do you plan on selling in the near future? In the latter case, you would be advised not to go overboard with the colors; potential buyers may not have the same taste and may be put off from buying.
The second most important point in planning a color scheme is the consideration of the quantity of light which penetrates into the room. The number, location and size of the windows should be carefully studied. It is needless to say that darkening a room by partially or completely covering the source of light will darken the appearance of every color in that room and often neutralize them, so a cheerful color scheme will be turned into an uninteresting or gloomy effect.