You can use a damp cloth and a hot iron to remove carpet dents. Lay the clean damp clothe over the indentation and place the iron on the cloth a few seconds. Keep the cloth nicely dampened. The iron may need to be there a few minutes but check after 15-20 seconds to avoid damage to some finer fabric threads in the carpet.
Also you can place an ice cube in each indentation, and let it melt. When the ice is gone, use the vacuum to pull the fibers back up to original shape. Use your fingers, also, to ruffle the fibers up. The finger massage helps the fibers return to normal faster. A towel placed on top of the dent usually follows a couple ice cubes in the dent left to melt. Then a steam iron is used. When you feel the carpet start to rise up, stop ironing and separate the strands with your fingers. Next use the vacuum to ull the fibers up.
Some times a wet cloth alone will do it. Make sure the cloth stays wet.
A garment-steaming appliance often will give the indentation enough moisture to become uncompressed. Also a steam iron can reverse the packed fiber dent. Watch to make sure carpet is not soaking wet. Then you need to rake through the fibers with your fingers or a fork or a rake designed for shag carpet. This raking will help life the fibers. The raking will help the carpet but not the padding beneath it. Only time helps with that dent. The steam iron helps to raise the padding beneath the carpet, which has been crushed. The moisture help to swell it. A soft hairbrush used in straight and circular movements also helps lift the dent.
Using a mist dies bit always work if the carpet is older. Also the type of carpet is important. After steaming the dent, using a fluffing pattern with rake or fork, even a hair pick can help. Also you can brush the dent from side to side, then top to bottom. It may take more than one session to get the result you want. A better move is to get the flat plastic or glass pieces to put under chair legs and couch legs etc.
Using a hair blower and comb to fluff up some of the plusher carpet types.
Some homeowners use a dog or cat brush to bring up the fibers. Brush the fibers toward the center of the dent.
A professional maid service recommends using a dry arpet cleaner on the dent and then run the vacuum in several directions.

Using an iron on the carpet without a towel or cloth can burn some fibers or maybe melt some areas. Keep the steam iron moving continually to avoid too much hot steam in one area. Leave the towel on the dent until it is completely dry.

Prevention of the indentation

The use of casters or furniture cups or glides will help avoid the problem.

Old timers would use the lid to the coffee can turned upside down, then place the caster on the lid to spread the weight over a larger area.

Moving furniture around a couple times a year also helps avoid these dents being made. Heat, moisture and hand fluffing are the best tools to raise the carpet fibers. If it is an old carpet with furniture in the same place for years, the indentations will not likely be raised to original shape.

These are some good tips about how to eliminate indentations in your carpet both by prevention and after care.