As a general rule of thumb, anything over an 85 on the ASVAB will qualify you for nearly any position in the armed forces. But there are slight breakdowns within each score. For example, in order to qualify for Surveillance and Communications (SC) in the Army, Word Knowledge, Paragraph Comprehension, Arithmetic Reasoning, Auto & Shop and Mechanical Comprehension all require high marks. Though scoring an 85 or above would guarantee you scored in a high enough percentile to qualify for SC.
To be admitted to the ASVAB testing room you will need to show a valid id. It is also important to be on time (or early!) since you will be turned away if you show up after the scheduled start time. The ASVAB can be given via computer or pencil and paper.  If you are testing at a MEPS site you will take it on a computer.  The pencil and paper version is given at most MET sites.  The computer version of the test is given as a "computer adaptive test" (CAT) which means that the test will adapt based on the level of the individual test taker (e.g., if you answer many questions correctly, you may be shown fewer questions).

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.