There are a number of partial solutions, but the most complete solution is a whole house humidifier attached to the air handler of your heating and cooling system. There are a number of limited solutions from boiling water to putting pans of water by your warm air supplies to using tabletop and console room humidifiers. If you choose to use room humidifiers, be careful to clean them and change the water regularly. Any humidifier, whole-house or room size, will require some maintenance. Some types, however, require more maintenance than others.