If possible, waterproof the crawl space before building the house. If the house is above the water table, consider building it without a basement or crawl space. If the house is located on a damp soil or if there is a lake next to the house, create exterior drainage and waterproof the crawl space on the outside of its foundation.
To waterproof the crawl space from the outside, coat the concrete with a waterproofing agent, and place some gravel at the depth of the foundation footing. In addition, build a tile drainage system to go around the perimeter of the footing. Place more gravel on top of the perforated plastic tile, and fill the rest of the space with topsoil. Obtain a sump pump with a battery backup, and place it inside the crawl space for consistent water removal.
Another appliance that can help to keep the crawl space dry is a dehumidifier. It prevents the air in the crawl space from getting too moist and therefore reduces the air ventilation of the crawl space. Moist air is dangerous for the house and the people living in it, as it induces mold growth. Another way to reduce mold growth is to place a polyethylene vapor barrier on the interior walls.