Without saying the obvious (get a humidifier and a dehumidifier) what troutie posted does work, to increase humidity clip a towell across a coat hanger above a bucket or tray of water, let the end touch the water so the towel wicks up the water. then use a small fan and blow across the towel. That will increase the humidity in the early stages.
To lower it without buying a dehumidifer keep the air moving with extra fans and place a dry towel in the room.
You may need more then one towel.