1. Map Your Plans
Whenever you think about rearranging furniture, the first thing to do is measure your space. Use a tape measure to find the dimensions, and then map out the room on graph paper. Don't worry about drawing in furniture at this point, but do include windows, doors, outlets, fireplaces and other aspects of the room that will affect its layout. Make a few copies of this layout, so you can brainstorm different options.
Using the layout of the room you created, start mapping out areas that you want to be used for certain activities. It's still too early to think about furniture at this point. For instance, if you pass through this room to get from one part of the house to another, draw a straight line between the two doors. If you want a place to play board games or cards with friends, draw a circle. In this way, you can get an idea of where to leave space open and what furniture you might need.
Based on these factors, start drawing in your furniture where you'd like it. Measure your furniture to get a better idea of how it will fit in the space. Go through a couple of versions, and in at least one, place something where you don't think you'll like it, just to see how that affects the way you arrange the rest of the room. You may stumble on a great idea.