At 18 years old (and under 21) anyone legally able to own a gun is able to open carry a gun in AZ. Open Carry means just that--OPENLY. A pistol should be holstered and apparent to casual observation that a firearm is being worn. Do not cover it with your shirt, do not cover it with your jacket. You may carry (and should carry) a LOADED pistol, with 'one in the chamber'.
Keep your gun out of places that serve alcohol for 'on premise' consumption (bars & restaraunts) [allowed only when concealed, with a CWP, and not posted as forbidden by the establishment]. Stay out of hydro electric plants, nuclear plants, voting stations, and off school grounds (no GFSZ in AZ).
While driving, the weapon must either be holstered, in plain sight, in a glove box/center console box, map pocket, or 'luggage'.