Visually plan out the room before you buy any furniture or room decorations. This way, you can plan out which pieces of furniture you want to be what color and where you want them to be in the room.
Choose the color of the walls for your room. This is another necessary step to do before you buy any of the room decor. Doing so will allow you to be confident that everything will match the way you would like them to.
Pick a different color rug than the wall color. If you pick a gray rug, pick a tan paint for the wall color. This sets a good base for the tan and gray hues so everything else will match and fall into place among the wall and floor backdrops.
Add different shades of tan and gray to add dimension and depth to the room and break up any monotony that may arise with the subtle, neutral tones that are tan and gray. Choose a darker gray sofa with a lighter tan throw blanket and dark charcoal gray lamps to pull the room together.
Use the same principle of adding different light and dark shades of tan and gray for any room you wish to decorate to let the room match and still have its own sense of individuality with the color dimensions.