There's a few basic rules to adhere to when planning your living room to make the most of it.
Scale. large furniture in a large room and smaller furniture in a smaller room. Sounds like common sense, but in my experience people get carried away in furniture shops, measure your room and measure the furniture you're buying. It'll save you a lot of time and money.
Sofa. The first piece of furniture to buy for your living room is your sofa. It's the largest piece of furniture in the room and will dictate the other furniture in the room as well as the style.
Focal point. There has to be a focal point for people to gather. It usually the fireplace or television but it can just be a coffee table.
Space. make sure you've got enough room to move around your living room. It's normal to leave 600mm to 1200mm (2 to 4 feet) to move comfortably around and this leaves enough room for daily traffic.