How Do I increase the humidity in my wooden and plexi-glass cages?

I have a Burmese and a Ball Python (House seperately), But I need to raise the humidity quite a bit. How do I do so?
(I heard putting a small plant intot he cage and watering it helps….. and also useing a spray bottle…… or setting a non-spillable glass of water in the cage..)

any other suggestions?