To get started, you need to ensure that you continue to qualify for active duty. You can contact your recruiter who can explain this process in more detail. 

Talk to military recruiters.

Your master hunter will tell you whether or not you have served or need to report to the ASVAB. Another thing your bounty hunter will tell you is that depending on the needs of the US military aptitude exam, you may be forced to return to the military and do your previous job. 

Sometimes, if you're lucky, they allow eligible ex-soldiers to sign hiring contracts for new jobs. However, if you are satisfied with your previous job, you will be asked to retake the ASVAB exam.

ASVAB is now computerized.

As a former member of the service, you will quickly find that a lot has changed in the ASVAB test. Gone are the days when you were sitting at your desk with a number 1 pencil and scrap paper and you were given an exam book. 

The ASVAB test is now applied to the computer. In the past you had to take an exam and then wait for the results, today you will receive your exam results as soon as you leave the exam room.

The basics you'll remember are still in test, but newer approaches have been added since the last exam. Remember to be prepared so you don't have to worry.