Place a straight-backed couch facing a bay window to create a cozy place to enjoy the view. This also provides a quiet sitting space that is separate from the rest of the room. Leave enough room at either end of the couch for people to walk around and sit down, which prevents wear on the back of the couch from people jumping over it to find a seat.
A low, straight-backed couch placed against the window seat of a bay window creates a sitting niche where people can sit out of the way of action in the room while still being observing or participating in it. Light will still stream in from the window over the back of the couch. Pull the couch out a couple of feet to create a niche behind it to store a bike or folding treadmill.
A curved couch presents interesting placement opportunities with either a bay or straight window. Face the couch towards the bay window to create a sitting circle, especially when the bay window has a window seat where people can sit to complete the circle. Turn the couch around so that its curve fits into the curve of the bay window for a separate but cozy seating area. Angle the couch towards one corner of a straight window to catch light without the glare.
Do not place your couch in front of a window if you would like to follow the practice of feng shui, which is a Chinese philosophy on how to promote the flow of chi, or energy, in a space. Feng shui design principles stipulate that a couch is the focus of the room and should not block energy exits such as windows and doors. The couch should reside in the corner the furthest distance from the door.