The specific requirements to become an army drill instructor vary depending on which country you live in, though you typically need to have a non-commissioned officer (NCO) rank, serve for a certain number of years, and attend a special training school. In the United States, army drill instructors are referred to as drill sergeants and are typically either Sergeants First Class or Staff Sergeants before attending Drill Sergeant School. To become an army drill instructor in the UK, you have to hold the rank of Warrant Officer class 2, though other non-commissioned officers in charge of training soldiers can also be informally referred to as drill sergeants. Army drill instructors in Australia are referred to as recruit instructors, and can be either commissioned or non-commissioned officers.
Each country has its own specific requirements and name for the officers responsible for conducting army drills. In the United States, the term drill instructor refers specifically to a US Marine Corps position. The US Army uses the Drill Sergeant rank for its drill instructors. General duties for these various positions tend to be somewhat similar, though the actual training methods from one armed services branch to another can be quite different.
The initial step to become an army drill instructor in the United States is to earn the rank of a non-commissioned officer. This can be accomplished by enlisting in the US Army and serving with distinction, exhibiting leadership qualities, and not requiring any disciplinary actions. You will typically want to be a Sergeant First Class or Staff Sergeant, though regular Sergeants are sometimes admitted as well. In addition to the NCO rank and a good record, you may also need to have four or more years of service.
In some cases, the Department of the Army (DA) will select someone specifically for Drill Sergeant status, though people can also request entrance into Drill Sergeant School (DSS). The term DA Select is used if the Department of the Army selects you, and you will typically be known as a volunteer candidate if you request entrance to DSS. If you are accepted you may attend the school, after which you can become an army drill instructor.
Throughout the course of attending Drill Sergeant School, you will undergo the same type of instruction that you will later be responsible for giving new recruits. This essentially means you will be going through basic training again. Since basic training can be very physically demanding, you will typically also want to be in peak physical shape before attempting to become an army drill instructor.