Picking the right humidification device is critical if you expect the tight white ash for which we burn.
There are two kinds of devices, active and passive (terms that may also sound familiar in the bedroom).
Passive devices are what most of us use. You fill them with distilled water, manually adjust the louvers and monitor the humidity using a hygrometer (digital preferred). When the hygrometer starts to dip below 68 degrees Fahrenheit, you know it is time to refill the device. I recommend a nice Diamond Crown brand humidifier.
Active devices require much less care. Simply fill the device with distilled water, set it to your desired humidity level (probably 70 degrees) and the device does all the work for you. As far as active devices, Cigar Oasis makes great ones.