When you go out to look for carpeting it's best that you do some homework first. Before you go to the store you should know a bit about the available carpet types you're going to be presented with. Have an idea of what each of the carpet fibers have to offer as far as durability and ability to repel stains.
Most wall to wall carpet is produced of man made fibers such as olefin, nylon, polyester, acrylic or blends of these fibers. PET is made of recycled plastic. PET is one of the strongest man made fibers and is stain resistant.
Acrylic carpeting is very similar to wool (wool is considered the best carpeting available) and is sometimes called man-made wool. It resists moisture, fading, mildew, crushing and staining but is not recommended for high traffic areas in the home. Nylon carpeting is popular due to it's durability. It resists mildew, staining and soiling. Nylon carpet is recommended for all traffic areas. It is one of the most expensive of the synthetic fibers but cheaper than wool. Olefin is a very low cost easy care material that is often used in indoor/outdoor carpeting. Olefin is colorfast and strong and easy to clean. One drawback to olefin is that it can be easily crushed depending on the pile. Polyester is luxurious and durable however is not good for high traffic areas in the home.
Another consideration would be the density of the carpet. You want a high number of fibers per square inch. A closely packed pile is an indication of a well made carpet. Check the carpet backing closely to make sure you don't see any bare areas.
The two most popular types of carpeting today are loop pile and cut pile. Loop pile has individual strands of yarn pulled through the carpet backing twice, creating a small loop. Cut pile has the loop cut at the top, leaving tufts of yarn that stand straight up. A cut pile carpet is generally more durable than a looped pile carpet. Cut pile carpets come in a variety of styles such as shag, textured, saxony and velvet or plush. Loop pile carpets would be a berber, cable or sisal. Loop pile carpets are a good choice for high traffic areas.
Ask to see the manufacturers performance rating guidelines on any carpet you are interested in.
Doing your homework before you purchase goes a long way to insuring you make the best decision. The old saying "an informed consumer is a happy consumer" hold true.