Seasoning a humidor is a crucial and necessary step ensure your brand new humidor functions properly - no matter how nice, how expensive etc. The inside of the humidor is usually lined with Spanish cedar, or in some cases mahogany. The reason these woods are used to line the inside of the humidor is they hold humidity well, and both woods contain a natural anti-fungal agent that resists mold. In any case, this wood has been kiln dried, and if you simply fill up the humidification device, this kiln dried wood would suck up all the moisture.

To season your humidor, you need to spray down the interior of your humidor with distilled water (use a clean spray bottle, on mist, for an even dispersion).   Thoroughly spray your humidor down and then let the water be fully absorbed into the wood. (I should mention that if your humidor does not contain any wood in the interior, then seasoning is not required.)  

After spraying down the inside of your humidor, fully charge the humidification device with distilled water and let it sit inside your empty humidor overnight.  Also place a clean sponge soaked with distilled water in your humidor.  Be sure to place the humidifier and sponge on top of a sheet of plastic wrap (or a clear plastic bag such as a sandwich bag) inside the humidor. This will prevent them from directly touching the wood, which could possibly leave a water stain.  Let the humidor sit overnight and check on it the next day.  If the humidity is low (less than than 65%), re-spray the humidor again with distilled water and let it sit overnight again.  Repeat this process until your humidor has a humidity level around 70% (but no more than 75%).  Once your humidor is capable of holding a reasonable humidity level steadily for several days, you are now able to store cigars in your humidor.  The humidity may drop again once your cigars are in but don’t worry, this is just the humidity adjusting to the addition of cigars.  Simply recharge the humidifier when needed and the humidity should stabilize after a week or two.

If after you've placed cigars in your humidor and it can't hold a reasonable level of humidity (67-74%), add a 50/50 mixture of propylene glycol and distilled water (50% water, 50% PG) to the humidification device.  (Add this mixture only once.  After this, only add distilled water to the device when you need to refill it.)  After a week or two (the mixture needs to stabilize), the humidity should be a perfect 70%.