Owning a humidor is a great way to preserve the flavour of your cigars and prolong their life. Before you can begin using your humidor, you need to do some prep work. You will need to season the humidor and assure the humidity levels are adequate to safely store your cigars.
The Seasoning Process
1st - Activate your hygrometer.
This will make sure the hygrometer can adequately measure moisture. Take a take a towel and get it damp. Use only warm water. Wrap the hygrometer in the towel. Set it aside for 30 minutes. Remove the hygrometer in the towel and calibrate it so it reads 95 to 97%. Each hygrometer will be calibrated differently. Refer to your manufacturer's instructions to figure out how to calibrate yours. If your hygrometer already reads 95 to 97% when you remove it from the towel, it is ready to use. You do not need to calibrate it.
2nd - Clean the humidor. If your humidor is new, you may not need to clean it. However, if you're preparing an older humidor, clean it out quickly before proceeding with the process. If there is any old tobacco or debris in your humidor, spray the inside of the humidor with compressed air. Wipe down the interior of the humidor with a damp rag.
Completing Preparation of Your Humidor
1st - Submerge the humidifier in distilled water. Most humidors will come with a small, circular humidifier. If yours does not, you can order one online or buy one at a tobacco shop. Fill a bowl with distilled water. Place the humidifier in the bowl so it is completely submerged. Keep the humidifier face down. Leave it submerged for 2 to 3 minutes. Wipe off any excess water with a paper towel when you remove the humidifier. Make sure you use distilled water. Tap water can damage a humidor.
2nd- Place a plastic bag and damp sponge in the humidor. Open your humidor. Line the bottom with a plastic bag. Get a sponge damp, using distilled water, and place the sponge on top of the plastic bag.
3rd - Install the hygrometer and humidifier. These are installed on the inside lid of your humidor. You should be able to figure out where to install by seeing where the pieces fit. If you're unsure, refer to your humidor's instructions manual. Once the hygrometer and humidifier are in place, close the humidor. Set the humidor aside somewhere where it will not be disturbed. Leave it closed for 12 to 24 hours.
4th - Repeat the process again. After 12 to 24 hours have passed, you will repeat this whole process again. Submerge the humidifier in water and line the humidor with a plastic bag and a sponge. Then, install the humidifier and the hygrometer and set the humidor aside for 12 to 24 hours. Once you're done, the humidity level should be between 65% and 75%. It may be slightly higher right after you complete the process. Give the moisture levels a few minutes to go down. Your humidor may not be between 65% and 75% after repeating the process a second time. In this case, you'll need to repeat the process one more time.
Caring for Your Humidor
1st - Store cigars properly. You should remove the paper wrapping of a cigar before storing it in your humidor. Cigars that are stifled by wrapping will not breathe well. This will prevent them from being seasoned and flavoured, which is the point of a humidor.
2nd - Limit how often you open your humidor. You want to keep humidity levels stable. Opening your humidor too often makes the inside lose moisture. Only open your humidor when you need to get a cigar. Take one out quickly and then close the humidor.
3rd - Remoisten as needed. A humidor's moisture level should be between 65 and 75%. Check the hygrometer once in a while to make sure that the level has not dropped. In the event the humidity has dropped, you will have to repeat the preparation process. You would remoisten the humidor the same way you initially prepared it. Make sure to use distilled water when you repeat the process. This is just as important the second time around as it was the first. Tap water can harm the humidor.
4th - Store your humidor safely. A humidor should be stored in an area away from sunlight. You should also keep your humidor away from heat or air conditioning ducts, as well as interior lighting. A good place would be in the drawer or another cupboard.
Source: How to Prepare a Humidor