The first step that one will take after deciding to pursue a career in the military is taking the Armed Service Vocational Aptitude Battery test. This is more commonly referred to as the ASVAB. The ASVAB not only determines whether or not a candidate is qualified to serve in the armed forces but also shows which specific job they have the most aptitude for.

Whereas recruits who join as officers tend to be upwardly-mobile,[14][15] most enlisted personnel have a childhood background of relative socio-economic deprivation.[16][17][18] For example, after the US suspended conscription in 1973, "the military disproportionately attracted African American men, men from lower-status socioeconomic backgrounds, men who had been in nonacademic high school programs, and men whose high school grades tended to be low".[14]

Each branch of the military sets an AFQT score requirement for applicants. The lowest qualifying score is 31, which is needed to join the Army. Higher scores are required for other branches of the military. For example, the Coast Guard only considers applicants with a score of 40 or more. Prospective recruits who have a GED rather than a high school diploma will, in most cases, need to score at least 50 on the AFQT.
The AFQT score is a percentile ranking between 1 and 99 that shows where your score is placed in relation to others. For example, if you score a 54 on the AFQT, this means that you scored as well as or better than 54% of other recruits. If you are not satisfied with your score and wish to retake the test to improve your chances at getting selected, you must wait a month before taking it again. You can retake the test as many times as you want, but after 3 attempts the waiting period jumps to 6 months.
With very few exceptions, becoming a non-commissioned officer (NCO) or petty officer in the U.S. Armed Forces is accomplished by progression through the lower enlisted ranks. However, unlike promotion through the lower enlisted tier, promotion to NCO is generally competitive. NCO ranks begin at E-4 or E-5, depending upon service and are generally attained between three and six years of service. Junior NCOs function as first-line supervisors and squad leaders, training the junior enlisted in their duties and guiding their career advancement.
The development of breech loading had the greatest effect on naval warfare, for the first time since the Middle Ages, altering the way weapons are mounted on warships, and therefore naval tactics, now divorced from the reliance on sails with the invention of the internal combustion. A further advance in military naval technology was the design of the submarine, and its weapon, the torpedo.
In order to take the ASVAB at a MEPS for enlistment purposes, an individual will need to speak with a recruiter and schedule a time to take the test. ASVAB testing at a MEPS is self-paced and taken on a computer, and it may be retaken after a one-month waiting period.  Entitled the CAT-ASVAB, the test is adaptive – meaning it adapts to your ability level.
The Student ASVAB is the most flexible of the exams. It is typically provided to high school students to help them assess their skills, job prospects, potential military positions, or college majors. The ASVAB for students is essentially the same as the MET ASVAB exam, only students are not necessarily testing for positions within the military. The students’ school counselors examine their scores and help them decide on what to do after graduating from high school. This test is still an important component of a student’s education because it can help them identify their strengths and weaknesses and help set them on the right track for their future career goals.