Tips on Rug Usage and Placement, Via HGTV:

When using one large rug in a living or family room, make sure that there is an even border of flooring around all four sides once placed, or at least so that borders of flooring opposite each other are even. Don't get a rug so large that it touches or rides up on the baseboard around the room.

If your room is formal with a natural center, it might be nice to use a rug with a center medallion design to accentuate the natural layout of the room.

Try using two rugs in one room to define different areas/functions within it. They don't have to match. In fact, it's more interesting to see coordinating area rugs that display some of the same colors, but vary the scale of the pattern and alter the design.

As a general rule, put the front legs of furniture pieces on the rug and the back legs off. More important, however, is to make sure the rug is placed in a balanced fashion in the room, and the furniture can fall either on or off of it.

The perfect size of a dining room rug is one that is four feet larger than the width and length of the table. As long as the rug is large enough to move the chairs away from the table without them falling off of the edge, the rug is the right size. Any surrounding furniture like the china cabinet or serving pieces should be on the floor, not on the rug.

Area rugs muffle sound and add a restful quality to any room. For the kitchen, hallways and entry, an Oriental rug is the best bet — no other soft floor surface is as durable to withstand the wear and tear of daily life. Plus, a wool area rug is easy to care for.

If your room has a definite focal point like a fireplace, it's usually best to go with a rug with an all-over pattern so it doesn't compete with or distract from the focal point.