The rooms natural focal point, Your eyes are drawn immediately to it.
This could a window/ fireplace/ bookcase.
If the room does not have one, create dynamics by using a contrasting rug.
The Furniture
Does the furniture satisfy the function the room is intended for?
From this example the furniture fits the intention of a living room.
Not everything will work together, experiment.
The Lighting
The direction of light suitable for function ? lighting creates a visual appeal?
Does a light bounce of a TV screen? if so move the light or screen.
Use lighting to brighten up rooms or to create an ambient feeling.
Change lamps around according to seasons if you like.
for example a winter feel add sprinkle lights and warm tones.
The Furniture Arrangement
Draw your room on graph paper. Measure and mark electrical outlets and switches, vents, windows and doors. Measure your furniture and place it in your floor plan. Generally, the main furniture pieces are directed toward the focal point, keeping the major traffic patterns open. Fill in with pieces you'd like to have that may or may not be available now. Be sure to balance high and low pieces as well as heavy and light ones around the room.