The question I get most often involves how to get started in a room. Sometimes the most difficult rooms are not the ones with the crazy colored sofa/rug/drapes/carpet, but the ones that have no color at all.
My first bit of advice is to take inventory of what you have. It could be a couch, a rug, existing drapes, or wall art. Paint is easy to change. Drapes aren't too difficult either. But start with one piece. For example, in the picture above, I had the sofa, loveseat, and rug. The couches were pretty neutral but had some flecks of rose, blue, and gray. The rug had blue and rose and cream. These became the colors to build on.
Next, find another piece that complements what you already have and starts to bring the colors out. In this case, I found the floral fabric to make swags that had various colors of rose and a bit of blue. This could have worked in reverse, if your sofa has lots of color - or a predominant one - find complementary colors to go with it. If the sofa had a pattern, pick a solid shade for the drapes.
Pick a color within your items for your wall color.
Finally, accent the room with other colors contained in your furnishings. I pulled out the deeper rose hues. The underside of the swag was the same fabric for the window treatments in the adjoining dining room. This gave a common element to pull the two rooms together while letting them have their own decor. The pillows and throws were to used to "spice up" the really boring furniture.
This method will make sure all the elements in your room coordinate - as well as between rooms if necessary. It's also an easy way to build your room's decor once you pick that one element as your anchor.