Well, first of all taking the asvab is like the sat/act. You can't really jump your score up. However, several common factors play. Time, rest, food, mind set. etc..
Id go to your library and study an ASVAB book. Find an area that you feel you are doing great in, and focus on the other areas.
There are several types of ASVAB tests, I would recommend you taking it at the MEPS center on the computer, and tell your recruiter you want to. Reason? the questions are in order on how well you did on the previous question. IE they get the harder ones out of the way first and give you time to focus on the questions you know well. you don't want to skip questions and turn in unanswered questions. You don't lose points for missing the question.
I would take as much time as you can working the practice tests, it also depends on what type of job you want to do in the Military? You have to take the asvab for entry in the military. You can do bad and still get in, however, your jobs are super limited.
Once you find what you want to do Intel, Computers, Aviation? etc. Then i'd figure out which areas of the Asvab are critical for that MOS. Ie, areas of General Science, Paragraph Comprehension, Word Knowledge, etc.
If you have several months, I think you should take the prep/ practice test several times on your own online. Get use to understanding the questions, how to pace your time for reading and all that.
Finally, when your ready. Make yourself ready. Get rest, eat well, focus, and always remain positive.
Good luck!
