Savanna, I would recommend that you take a practice test first, to see where your strengths and weaknesses are. A recruiter may be able to give you a real one, or you can find an ASVAB study book or on-line resource. You also need to know which tests are important for the career you are hoping for. Those are the ones you need to study the most. For example, if you want to be in the legal field, you may not need a high score on electronics. Work a little bit to make your strengths stronger, but, work a lot on your weaknesses! Look for study guides outside of military guides. For example, if you are weak on math or vocabulary, use the ACT or SAT study guides. Seek to truly understand, rather than memorize.
Now, a trick. This is no substitute for studying. It's just a way to boost your score 2-5 points on multiple choice tests. If I were to give you a 10-question true/false test in French (or some other language that you do not know), what answers would you give me? Think about this a minute before reading further. . .
If you randomly mark true and false, you stand to miss every question. But, if you put all true, or, all false, you will likely get 4-6 correct! What's the point? When I walk into a multiple choice test, I have a letter in my head. Today, I pick "B". For every question I do not know, and cannot narrow down, I will put B and move on. Lowers the stress level! Also, if I am about to run out of time, I will mark every remaining answer "B". A few of those will likely be correct! But wait, suppose I can narrow it down to A or C? Or C or D? Now what? If I cannot come up with a definite answer, I am going to pick the option to the furthest to the left. The first one is A, the next one (above) is C. Again, lowers the stress level, and lets you perform better on the rest of the test.
I explained this to a relative who had twice flunked the ASVAB. The third time, his score went up so much that they made him take it again, fingerprinting him for positive identification. Again, he got a much higher score than the first two times.
Actual study techniques vary person to person. I like vocabulary flash cards. Some people don't. I also like learning the Latin/Greek root words, and trying to visualize things. Obviously, study only when you are mentally alert, not when you are tired.
Wishing you the best!