Carpet Cleaners suggest you fill a spray bottle with water and spritz it over the dents. Then use a blow-dryer, on the hottest setting, to blow air over any moistened areas. (The heat helps wool and nylon carpet rebound.) Fluff up fibers with your fingers.
My personal favorite is put an ice cube in each indentation, and let cubes slowly melt. Wait 12 hours, blot up wet spots, then use the edge of a spoon to lift carpet fibers back up. Or steam away dents: Place a clean, damp cloth over them and hold an iron, on medium heat, several inches above the cloth for about 30 to 60 seconds. Don't let the iron touch the carpet -- it could burn! Brush up fibers with a coin.