I think the biggest struggle for most people is figuring out how to arrange furniture to get the most out of a room. With a living room or family room you want to make it easy for people to hold conversations and to be entertained as well. Over the years I've learned that you have to pick one main focal point in the room and work off of that. Either that be a fireplace, T.V., painting, or a killer view; you want to have it be your main attraction. This idea works for more than just a living room or family room. Take the idea into the bathroom, kitchen, and bedroom. Whatever you choose to be the main focus is what others will automatically look towards when they walk into that room.
One that can be tricky is having two focal points in one room. A lot of family rooms have a T.V. and a fireplace. This is perfectly fine, arrange furniture in a way that both could be seen and enjoyed with out the other being a distraction. Below are some examples. Have fun decorating!