A: Yes, mounting to the lid works best. Soak the humidifier in distilled water, then drain the excess. Using tap water is asking for problems, stay away! A hygrometer is not necessary, but it is a good thing to have. Especially if you don't want to constantly check up on your stash. I would recommend a digital hygrometer, as they tend to not only be the most accurate, but provide years of reliable service. A good one will cost around $15 (well worth it when you take into account the headaches you could save yourself).