Depends on what you have retained from high school. Best advice I can give you is do not get hung up on any one question too long. Answer what you can in the section you are being timed on then go back and try to answer the rest. When you are going to run out of time fill in all the questions you could not answer with something. But do not jump around with your answers. For intance lets say there are 10 math problems you could not answer. Fill them all in with the same letter, such as C. If C is what you are picking to fill in questions you do not know then sick with that lanswer for all the ones you can not get. Do not leave anything blank.
find a "asvab for dummies" or some sort of other asvab review book(find them used on amazon for less than $5) and study for about a month before hand. i've been out of high school for 12+ years, yet did a few practice tests and reviewed long division, math skills for a couple weeks prior to the test and i did awesome. put the time in and things will work out for you.