To properly care for your cigar collection you will need a humidor. Ideally, the interior of the humidor will be made of Kiln dried Spanish Cedar and will have a tight seal. A good way to test the seal on your humidor is to hold the lid open approximately 3 inches and let go. You should hear a "swoosh" as the lid falls closed. This sound ensures a tight seal as the air inside of your humidor is forced to escape rapidly when the lid is closed. Along with your humidor you will need a hygrometer. The hygrometer measures the humidity level inside of your humidor. Finally, you will need a humidifier. The humidifier is usually a sponge type device, which you fill with distilled water. The purpose of the humidifier is to provide humidity by retaining moisture. The perfect conditions for a cigar are 70% humidity and 70 degrees Fahrenheit. Temperature and humidity are critical in keeping your cigars fresh.
Credit: CigarHandbook.com - Your Guide to Cigar Smoking