Select an appropriate rug. Choose one that corresponds not only to your overall decor, but also to how you will use the space. Pick thick, denser rugs for low-traffic areas -- these types will show wear and tear faster than others, so placing them where there's a lot of foot traffic will make them look old and dingy very quickly.
Choose smaller area rugs instead of larger ones -- they can be used not only to cover floors, but also to designate space. Put a circular rug underneath a bistro table, for example, to reinforce the idea of an "eating area" in an open floor plan. Place multiple chairs on a square or rectangular rug to designate the space for socializing.
Put rugs on the walls to use as decorations. Place them above couches as conversation pieces, in long hallways to break up boring walls, or even in kitchens to create a bright and colorful eating area. Place the rug away from where food will be cooked if you choose the last option -- otherwise, your precious rug may become splattered during meal preparation.