I'm a big proponent of actually trying out a new configuration each week for the first month or so, for a living room. You'd be surprised how different it actually feels with furniture in different spots, but most people tend to just place it when they move in and leave it. Living rooms also tend to be fewer furniture pieces than a bedroom or office, so more feasible to re-arrange.

This will also really help identify where your tv should be placed, to minimize glare or reflections.