"Is it possible to prepare for Intelligence tests?"

An Ask Metafilter question. The main piece of advice over there is exactly what you would expect: take practice tests. I'd add my classic piece of test-taking advice that I figured out by my own trial and error: Believe -- even if it's pure delusion -- that you're having a wonderful time taking the exam. Control your emotions. If you believe this test is going to destroy or embarrass you, you're doomed.