Rugs are one of the most important elements of any room in which they are used. They are the framework of the floor, providing percieved pathways for any room they are used in.
The most common use of a rug, is to provide a focal point for a space. If you have a huge room with floor space sprawling in every direction, a rug can concentrate the focus and bring everything together.
In smaller rooms, rugs are often used to add detail and interest, without taking up shelf or floor space.
The colors and patterns found in a rug are very important. If you are starting with a blank room, idealy the variouse colors found in the pattern of your rug, should be the colors you use throughout the space. If the rug is monotone, then contrasting colors should be used throughout the area.
Before you go out and buy a rug, try to get samples of its pattern or colors, and test them out in the room. Try living with them for a couple of days, each day looking on them with fresh eyes, before you make a decision. Sometimes you fall in love with something at the store, only to get annoyed by it a few days later.
There are a number of stores online which offer you literally thousands of different types of rugs. You can go to the variouse sites, print out photos of their rugs, and use them to see what the actual piece will look like in teh space.
The only problem with online stores is that you can;t get a real idea of how the rug wil feal and how it will wear. For that, you should visit stores where you can actually touch various materiuals, in order to get a good idea of what you are buying. Pay attention not only to how fluffy a rug is, but also to how much dirt it looks like it will retain, or show.