Humidifier

The humidifier thing isn't something I've ever encountered and sounds like baloney to me. IME usually guitars come from the factory with dessicant bags (dehumidifiers) in their (store) storage box. Although that said, you do live in Phoenix AZ. Been there. Know how dry the air is, so using a humidifier in your climate might have some regional WX extreme relevance [u]in longer term storage[/u]? Ask [u]the other guy[/u] at your LGS "Why?".

Tuning

You should check your guitar is in tune on every occasion you pick up your guitar to play prior to playing. Until you develop and ear, you will [u]need[/u] a tuner. You can use this tool here as a reference to tune by ear.

There are numerous tuners available in the marketplace including free Android app tuners. I've used Fender's on my Android phone in the past and it's easy to use and pretty good. You can get it here.

That said, most people including myself use inexpensive electronic headstock tuners like this for everyday tuning if for nothing else their sheer convenience.