Shop for carpet cleaners from such trusted brands as Royal, Sebo and Riccar.  Choose either a wet or dry system.  The wet system applies a cleaning solution to the carpet, agitates the carpet with a rotating brush, rinses with water and vacuums the dirty water into a collection tank.  The dry carpet method starts with application of a pre-treatment spray to high-traffic areas and stains, followed by sprinkling of a special cleaning powder on the carpet.  The carpet cleaning machine agitates the powder into the carpet, releasing dirt which is encapsulated by the powder.  After a half hour period, the powder is cleaned up with a standard vacuum.