An area rug is the perfect finishing touch for a room. When chosen correctly, the room looks polished and complete. If you choose the wrong rug for the space, it can look sloppy or hastily done. There are three elements to think about when choosing your rug:
Start with choosing the right size for the room. A good rule of thumb is for the rug to fit the seating area of the room you're working with. In an ideal situation, the furniture in your seating area (dining room, living room, etc.) should fit completely within the boundaries of the rug. If this isn't possible, at least the front feet of the furniture should be on the rug.
A quick note on shape: use a circular or square rug in a square room, and a rectangular rug in a rectangular room.
There are fewer rules for choosing a color than for choosing the size. You can decide if you'd like the rug to be a stand-out focal point, or blend in with the rest of your decor. If you're using a lot of color and different patterns in your room, solid will be your best bet. Browse through sites like House and Pinterest to find a style that works for you.
First, consider how much traffic the room will see, both for texture and as a tripping hazard. If you're choosing a rug for the hallway, you'll want something flat and woven with a wear-resistant texture. If your rug will be in the formal dining room, you can get away with a tufted rug or even an antique. The rest of the decor can guide you - try to pick something with a nice contrast to the room. If your furniture is sleek, a softer rug will look great. With lots of plush and soft furniture, a more simplified texture will be a nice change.