Don't Forget Your Living Room
Just because you're decorating for a space that's outside of your home's living room doesn't mean you have to forget the principles behind designing a social area. When most people set up a living room, they don't position all of the furniture against one wall -- they may place a sofa against one wall and a love seat against the opposite wall to create an area where people can sit and talk.
For porches and patios, it's easy to forget this concept and simply push all of the furniture up against the house, so that everyone is facing away from the house when sitting down. If you add an extra couch or set of chairs that face the house, suddenly all of your guests have a chance to talk to each other, play cards or enjoy dinner in an outdoor space that has the comfortable, intimate feeling of a living room.