Humidifier- This helps moisten the lungs. Putting it in the bedroom at night is best, as long as it does not make you too hot. The warm air humidifier that boil the water are better than the cold air ones. The cold ones more easily get moldy.
Take fish oils- This will help to slowly moisten your body from the inside out. The same concept applies to oily foods such as avocados, nuts and seeds and olive oil. Foods which are overly hot and spicy and the like will work against you.
Drink water- Plenty of it, at least two liters per day for adults living or working in a dry environment. Sure, you may pee most of it out, but little by little, the body gets more hydrated.
Saline nasal rinse- A saline rinse is a good way to keep the sinus cavities moist.