Inspect Your Room - Look around the room you want to rearrange. What do you have/want as focal points? If you have a fireplace and a television in the space it may be hard to choose. This is why a lot of TVs are mounted above a fireplace! However, you can have two separate focal points if your furniture can work with that. Maybe have a lower lying bench in front of the fire place for close up warming of your toes. If it has no back, you can still see the fireplace from any angle in the room. Just don't have it too close. Having your TV mounted on the wall, or in a corner can save on furniture space and if it is tilted right, can be viewed from anywhere in the room. If you have a window with a view, don't place bulky furniture in the way of the window. Either separate chairs, a console table or maybe that is where you want the bench! Just take your time to think before you start moving it all around!
Floor Plan Function - Along with viewing power, you need to be able to walk easily in your room, not to just get to the furniture, but, if you are in and out a lot, you don't want to always have to walk all around the room to one entrance of your furniture. Have several easy ways to access the area so people can easily move around and sit comfortably. Sometimes a back of a couch will act as a "wall" to divide spaces, but just make sure that "wall" has two doors around it, other wise what's the use in having an open concept? It won't feel like it's open, if it's difficult to get around a specific piece.
All Around View - View the space from all angles. You may not have considered what you furniture looks like from behind or the side. Maybe put that lovely patterned chair that is beautiful from all viewing points with it's back to a another area so that looking at the back of a chair will be more interesting than the solid fabric on your couch.
Details Matter - Little details in the space will make it more charming if you add little accents to different areas that you see. Small knick knacks or wall hangings that go with the seating in a specific corner, color choices that accent the room in several different places and a mix of patterns and textures all over add interest to a great floor plan. Experiment. You will find what works best in your home for your family.