You need to place the furniture so it will accent the focal point of the room, whether it be a fireplace or a built in of some kind but be sensitive to the traffic pattern. The mistake most people make is to push everything against the outside walls.
How the room is used dictates where all furniture is placed. Imagine the room at its normal occupancy, imagine where people are sitting, and where they are walking around. Since the entrance needs to be kept clear, there are a finite number of possibilities that can be counted on one hand, and one of these is likely to be optimal.
For example, my living room is the theater room, therefore the largest wall becomes the viewing surface, and that dictates that the seating furniture is pushed up against the opposite wall. There is no other configuration possible.