Before we begin there are a few points that need to be considered. A living room is always a transition space. This means that entrances to all other rooms are located in living room. Other bedrooms, dining room, kitchen etc. are accessed through living room, that's why a sufficient "circulation space" for family members is a must.
So here is what you can do to create the most efficient layout for a living room.
1) Take a plane white paper. A4 size is also enough.
2) Draw a sketch plan of your living room on this paper. While drawing this plan it is important to show the following things in it:
a) Entrance door
b) Entrance doors to other rooms
c) Window positions
d) Minor column projections (if any)
e) Swing of the doors (inside or outside the living room)
f) Presence of staircase
g) Fireplace (if any)
3) Take a pencil and draw lines starting from entrance door to all other doors and window positions. This is the natural travel lines for any person using the living room. If the room is empty without any furniture these are the lines any person would follow to reach other point in the living room.
4) Now start placing the furniture units like 3 seat sofa, single/double seat sofa, coffee table, end tables lampshades, bookshelves, TV unit, etc.. Depending upon your budget you can go for any number of these units.
While placing these units it will always be seen that the furniture obstructs the pencil travel lines drawn in the third step. But that's OK for now. Now make as may combinations and arrangements of the furniture units as possible. Think out of the box while doing this. Try to do something different.
Remember if you try you will easily come up with at lest 10 layout for that same living room. You will be amazed at how many combinations are possible. Also imagine the furniture pieces you already have or can you replace that table in the bedroom with the one in the living room.
How about keeping it vertical rather that horizontal in the plan. Whatever you do keep one thing in mind. Always keep the human movement "unobstructed". People passing through the living room in other rooms must be able to pass without cutting vision if you are talking to other person in the living room.
That's why those pencil lines have been drawn. After you have drawn the furniture pieces on the living room plan, modify the travel lines. Now these lines will be around the furniture, especially at corners. The travel lines will now take the shape of the furniture at the edges.
After this short exercise you will have probably 5 different layouts on paper with. Select the one in which you see the following points of interest.
a)Travel line lengths are shortest.
b)Travel lines do not pass trough the furniture.
Apart from the efficiency there is another factor called as visual balance while designing a furniture layout. Finally does it look good to YOU. Are you comfortable with the final layout. The visual balance is achieved by making the most use of all walls of the living room with decorating elements such as paintings, color schemes, etc.