When Push Comes to Shove
This isn't always the case, but some people try to push all of their furniture against the walls to attempt to make a room look larger. This can be a good tactic for maximizing center space, but more often than not, this is not the best move for establishing a comfortable environment.
Don't Back Yourself Into a Corner
If you have an already larger room, or if that room has a lot of natural light pouring into it, you might want to consider putting your furniture in the center of the room. When there is a lot of center space in a large room, people can feel estranged from one another. Don't worry, the back of your couch isn't THAT ugly.