I will be taking my ASVAB soon. What are some ways I can freshen up on general science?

Walk in to any Barnes and Noble and buy an ASVAB prep book.

It's not a hard test, but i can't stress how important it is to take it seriously. You'll only get one shot at it

You can go online and find a number of study guides and practice tests. Take a look at some of them, there are several free ones.