Stormtroopers apparently use the same rank system as the Imperial Army, but rarely wear any type of outward insignia. It is mentioned that Stormtroopers most likely have an identification scanner, built into their helmets, which can determine the rank and seniority of other stormtroopers.

The Stormtrooper Corps, also referred to as the Trooper Corps, was an autonomous military branch operating under the Imperial Army of the Galactic Empire. The Corps was best known for its extensive supply of elite and disciplined stormtroopers trained at academies across the galaxy, as well as...

In terms of the standard class of troopers, though, the highest rank that wears the suit is the chief. In canon, the chief often leads the action and fighting side of the military operation...

They are hand-picked from within the ranks of the Stormtrooper Corps, and are given extensive combat training at the Imperial Royal Guard Academy on Yinchorr. Those who survive the training, including a battle to the death, are permitted to join the ranks.