Start with the feeling you want to come home to. Dark, atmospheric art brings intimacy; an open landscape offers room to breathe. A horse or bull can express a sense of freedom or resolve. Choose the work you connect with, then let it set the tone for the room.
Above a sofa or console, use the furniture as your reference: artwork around two-thirds to three-quarters of its width is a useful starting point. Mark out the dimensions on the wall before choosing your size and finish.