Brush the carpet nap against the grain of the indentation with a toothbrush. Push the toothbrush as deep as you can into the nap and brush briskly. For a large indentation, such as that left behind by a heavy home entertainment center, you can use a stiff broom instead of a toothbrush.
Rent a commercial carpet steam cleaner, or use a home carpet steam spotter if you have one. Do not add detergents to the steam cleaner tank; fill it only with hot water.
Follow the manufacturer's operating directions and run the steam cleaner over the imprints several times.
Allow the areas to partially dry, and brush the nap against the grain of the imprint with the toothbrush or broom. Allow the rug to dry completely.
Evaluate the results after the carpet is dry. If the imprints are still conspicuous, work the spot again with hot water from a spray bottle and the toothbrush. Spray hot water directly into the base of the nap, then pull the nap upright with your fingers and hold it. Brush the nap into the proper angles with the toothbrush. Allow the carpet to air dry. Repeat if necessary.
Restore shallow, circular imprints caused by light furniture with ice. Place a couple of ice cubes in the indentation and allow them to melt. The slow infusion of water over a span of time induces the carpet fibers to swell and separate. After the ice has melted, blot the area dry with paper towels and vacuum the imprints to restore the fibers to an upright position.