Spanish Cedar
Spanish cedar is the preferred humidor lining because it works the best to absorb humidity within the humidor, it protects against tobacco worms and your cigars will age and taste better.
American or Canadian Red Cedar
American or Canadian red cedar is less expensive than Spanish cedar and is used many times for that reason; however, it does not absorb humidity as well, and if you store your cigars for a long period of time within the humidor, they will have more of a woody smell to them.
Honduran Mahogany
Honduran mahogany works as well as Spanish cedar when absorbing humidity; however, because the scent is not as strong as Spanish cedar, it does not keep away tobacco worms as well, nor will it create the same flavoring found in Spanish cedar.
Hygrometer
The wood inside the humidor is very important, but you also will need a hygrometer to check the humidity levels within the humidor. The hygrometer can be attached to the inside of the humidor and looks like a round dial.
Humidifier
The humidifier is important as well at keeping your cigars moist and so that they don't dry out. You add water to the humidor periodically, based on the hygrometer readings.