Basic design rule of thumb for a living room, the goal is to create a conversation area that is comfortable, inviting and not intimidating. The biggest mistake people make is just put furniture along each wall with no thought.
A traditional conversation area consists of a 3 seater sofa, and either a love seat (2 seater) or 2 arm-chairs.
The pieces should be placed either across from each other or at a 90 degree angle, close enough so when you sit there with a guest, you don’t feel like you need to shout for the other person to hear you.
You should also be able to place your drink easily on the cocktail table in-front of you or beside you, without having to get up. Many people make the mistake of having a tiny coffee table and place the sofa too far to reach the table.
The rug should cover the complete floor space within the conversation area. Designers use a rug to define space and make the room feel cozy. If you have a very large space, you may want to have more seating, perhaps 2 sofas and 2 chairs, in this case you will probably need more than one cocktail table so we need to get creative, with a bench or 2 ottomans, and a coffee table on the other side.
Same rules apply to the family room, if you have one. If you have both, I like to use more formal furniture in lighter colour for the living room, and leather furniture for the family room, where you may have you TV set up and spend more time lounging around with your family.