Figure out which areas to focus on based on your career goals. If you’re not interested in a job requiring a score on the Mechanical Comprehension subtest, you don’t need to worry about doing well on that subtest. If you don’t need to worry about mechanics, don’t bother preparing for that section. Spend the time on Word Knowledge or Arithmetic Reasoning.
The ASVAB site goes on to explain that “after the final ability estimate is computed, it is converted to a standard score on the ASVAB score scale that has been statistically linked to the ability estimate through a process called equating. Equating studies are conducted for every paper and pencil ASVAB form to ensure that scores have the same meaning regardless of which test form the examinee receives.”
Every single individual that goes through the enlistment process should excel both mentally and physically. That is the number one principle that has consistently inspired this nation to serve these brave and honorable individuals with unwavering efforts. Those efforts officially came to the forefront when the country as a whole decided to correct perhaps the most significant enlistment related problem (passing the Armed Services Vocational Aptitude Battery test). Countless hours of hard work and dedication are currently reflected by the top-of-the-line ASVAB practice tests that this nation offers.
As of 2017, the U.S. spends about US$610 billion annually to fund its military forces and Overseas Contingency Operations. Put together, the U.S. constitutes roughly 40 percent of the world's military expenditures. The U.S. Armed Forces has significant capabilities in both defense and power projection due to its large budget, resulting in advanced and powerful technologies which enables a widespread deployment of the force around the world, including around 800 military bases outside the United States. The U.S. Air Force is the world's largest air force, the U.S. Navy is the world's largest navy by tonnage, and the U.S. Navy and the U.S. Marine Corps combined are the world's second largest air arm. In terms of size, the U.S. Coast Guard is the world's 12th largest naval force. 
Many high schools give students the opportunity to take the ASVAB as part of career exploration. If you chose not to take one in high school, then you will have to schedule a time to take it. You can contact the Armed Forces Recruiting Officer in your area and you can schedule an appointment with a local recruiter from the branch of the military you wish to join.
Since 1976, the multiple-choice ASVAB has been used for initial aptitude screening as well as MOS classification. The exam has changed since its inception. While some parts have remained, such as arithmetic reasoning and word knowledge, others like tool knowledge have been removed in favor of questions related to assembling objects. After nearly 20 years of research and development, a computer-adaptive version of the exam was implemented in 1996. The CAT-ASVAB is the first large-scale adaptive battery test to be administered in high-stakes environments like a Military Entrance Processing Station. The paper and pencil, or P&P version is still used at a variety of other military testing sites.
One ASVAB sub-measure, the Armed Forces Qualification Test (AFQT)--which is just a separate analysis of the same tests that focuses only on four of the subtests--is also population-referenced, but its score from 1-99 is a percentile score. This means that if you score a 73, you scored as well as or higher than 73% of test-takers in the national sample.