Measure how much space you have for the artwork. If you're planning to put a painting or photo above the couch, for example, measure from the couch to the ceiling and take the results with you when you go shopping for art to ensure a good fit. Take photos of the room while you shop for even more accurate assessments while you shop.
Choose art that will complement the style of your decor. For example, a metal wall sculpture might set off a contemporary living room nicely, while delicate watercolor paintings could work in a country motif.
If you fall in love with a piece of artwork, arrange the living room to fit it. For example, if you must have that large photograph, arrange furniture, TVs and other items in the room so that the photo will have a wall large enough to showcase it properly.
If you want the artwork to to blend in with the living room, choose a piece whose size works with the space allotted for it. For pictures or photos, choose frames that blend well with the wall color for a cohesive look.
Widen your search beyond paintings and photographs. Consider less common home artwork such as wall or free-standing sculptures or collages.
Set a budget. Keep in mind that the more elaborate the piece, generally the higher it will be in price.