To keep soil and dirt off your carpet, or at least trap some of it before it gets tracked inside, place floor mats just inside your doors. It will also help if you have a mat on the outside entrance.  

A vacuum cleaner with a beater bar or a rotating brush will help loosen dirt trapped in your carpet pile and keep dirt at bay and deep clean your carpeting. How often? You can never vacuum too often. Remember, carpet sweepers are great for picking up crumbs and visible pieces of dirt. However, they will not deep clean your carpet.

Professionally Clean Your Carpet Every 12 to 18 months. 

Whether you use a local professional carpet cleaning service or rent a carpet steamer from the hardware store or grocery store, you’re adding life to your carpet by washing the dirt off the pile and deep cleaning. If you do rent a machine, make sure it has strong vacuum power to remove the water from your carpet. It should dry within 6 to 12 hours. Getting it too wet can damage your carpet and risk bacteria or mildew growth. You can always use fans or a dehumidifier to shorten the drying time. 

When choosing a cleaning solution, make sure it has a pH of 10 or less. Alsop make sure you remove all the detergent once you have cleaned the carpet. 

If your carpet is under warranty or has had stain resistance guard applied, you may need to clean with a certain or recommended cleaner/soap.

Use a dull knife or spoon to remove any solid materials. Blot up liquid spills with a white towel or paper towel. Never rub or scrub with a brush. This may cause damage to the carpet fibers. Use the manufacturer recommended cleaner for your specific carpet. Apply cleaning solutions to the cloth rather than directly to the stained area to avoid saturating the carpet when spot cleaning. Clean the fibers, not the backing. If the stain is deep, you may need to repeat the process.