Determine how large of a dehumidifier to buy. The larger the dehumidifier is, the better it will be in controlling humidity, especially if your basement is large. It also may be necessary to purchase more than one dehumidifier, depending on if you have multiple rooms in your basement.
Place the dehumidifier in a central location in the room. Be sure that there is no furniture surrounding the dehumidifier, as this will help with circulating the air. A dehumidifier usually comes with an attachment to place a hose on the unit itself, so the water it collects can be drained on a regular basis. The water can also be collected in a tub inside the unit.
Keep as much moisture out of the air in the room as possible while running the dehumidifier. This includes closing all windows and sealing any areas where air from the outside leaks through. This will aid not only in the operation of the dehumidifier, but overall so mold does not have the chance to grow.