You must first decide whether or not it would be appropriate to place an area rugin that room. If the room is much to crowded you may want to avoid making the room appear smaller by adding more things within the room.
Next you will want to decide what would be the appropriate sized rug for your room. Are you trying to place a rug under a piece of furniture? Or is the rug serving as a decorative piece in the center of a room. A rug is not meant to cover the entire floor of a room. You will want the rug to cover some of the floor but still leave a good majority of floor clear.
Next you will want to decide upon the color of the rug. This does not have to be a solid color rug. It should have several different colors which can also match other things within the room. The rug should be able to compliment the colors found in the pictures and other furniture found in the room.
When choosing the style of the rug you should pay attention to the other accents within the room. The theme of picture should also be representative of the area rug.