All agencies use different tests. There are some agencies who attempt to use a standard test, but there are more than one of those. If you're trying to just strengthen your test taking in general, I'd use a ASVAB study guide. It kind of covers the bases of math, reading, word comprehension, ect. I would also look into some brain game where you're matching pictures and being able to figure out directions on a map. Those will help you out if you run into the test that pointblank4445 mentioned. Some of these tests are written in house so be familiar with some stuff the agency you're applying for might deal with. For example, Customs might test you on some bigger numbers, state agencies might use a lot of fractions, and Border Patrol might test you on Spanish or their version of the DLAB. Make sure you look up as much info you can on any agency you might test with and use that as your guide for what you think you might want to study in preparation for their testing/hiring process.