If wanting to become a military training instructor, you must first join the military. All branches of the service use military instructors to educate and train military personnel. Once in the military, and having completed initial training requirements, those wishing to become a military training instructor must show the proficiency to be capable of instructing others in a given task. Having demonstrated the superior knowledge of a specific task, you will need to request a transfer to a training brigade and subsequently a post that requires the services of a training instructor. If you wish to become a military training instructor for a basic training cycle in the U.S. Army, the requirements are that you must have attained the rank of E-5 and been accepted into drill sergeant training school, which you must apply to through your company commander's office.
It is common for a person who has completed basic military training to wish to become a military training instructor. Having attained the skills and knowledge to complete basic training, many military enlistees wish to share their expertise and give back to the future soldiers. The typical protocol requires both time in the service as well as a specific rank attained before anyone can become a military training instructor. Following the chain of command, all of your superiors must agree that you are fit for the position, and your request will need to be put through appropriate channels.
Should you decide to make a career in the military, at a certain point in your military career, most branches of the service will typically require your to either become part of a recruitment staff or become a drill instructor. This requires that you meet the position requirements, and if you fail to meet the requirements, your tour in the military will likely be coming to an abrupt halt anyway without having the promotion points and proper standing to move forward. If you wish to become a military training instructor, your preparation should begin in basic training to ensure that you complete all of the required steps in the proper order.
You will want to talk to your training officers once you enter your permanent party or duty station to ask for the proper guidance in reaching your goal of becoming a military training instructor. By requesting as many training courses as you can attend and by excelling in every aspect of your training, attending drill instructor school should be easily obtainable. If you slack and simply do the bare minimum to get by, you will likely never be considered training instructor material.