1) Re-arrange your furniture for a no-cost update. Change the location of your largest piece of furniture. This is usually your sofa. Move it away from the wall, place it opposite where it sits now, move it perpendicular to where it is now...your room dimensions will guide you. When that's done, work the other seating pieces and tables around its new position. In this space, instead of having the sofa face the fireplace which is a great position for the winter, the chairs are moved to flank it, leaving a generous space open and changing the perception of the room.
2) Break your room into multiple seating areas. Consider separating your sofa from lounge chairs in a large living room rather than having a rectangle or circle of seating. Try creating a reading grouping in one corner, which can be both functional and attractive. When you use the living room for large gatherings, your new seating groups can be rotated into "conversational mode". The room in this photo had the settee in front of the fireplace. Changing the position and separating the dining table now gives two separate areas.
4) Bring an area rug into the space. A simple sisal rug from an import store can change the character of a space. It adds a light, summery style and with some re-arranging, your room can be transformed. The rule to follow for size: all of the furniture legs sit OFF the rug or all of them sit ON.
5) Drape fabrics over existing window treatments. In windows that don't get used much - so you don't have to fuss as you use them - add fabric panels to hard treatments like blinds and shades. Have fabric already? Add a square over the top to change it's color and style. Here, a simple Roman Shade becomes a country-style window treatment with a colorful napkin draped over the top. If you have old panel drapery, you can add a new header or hem in a contrasting and updated fabric.