A second way to care for your carpet is to limit the amount of dirt and debri that enters your home in the first place. A good quality doormat will do wonders in this regard. I recently purchased a new doormat made from recycled tires that I have been very impressed with. Whether you go with a traditional coir mat, a rubber based mat, or something more decorative, you will be doing your carpet a favor.
Lastly, have your carpet steam cleaned by a professional who uses a truck mounted machine at least once a year. Not only will this help your carpets last longer and improve the air quality in your home (carpeting is the largest air filter your home has), but annual carpet cleaning is a requirement for the manufacturer's warranty to cover your carpet from premature wear.
Do these three simple things and you will not only have a cleaner home but your carpet will last longer as well.