While many concerned students or parents shell out large sums of money for test preparation services, the real key to success on a standardized test is simply practice. Barrons sells an exceptional set of prep books that give solid strategies besides having sample tests to practice on. However, it is better to work from multiple books to get more sample tests. An easy way to save money on solid test preparation is to go to your local public library and check out books on test prep for your particular test.
More important than your expertise on the subject material is how you prepare. Test-taking is itself a skill, and more often than not the difference between average and exceptional performance is a matter of how well your mind is functioning on a particular day (which can be controlled to some extent by eating a healthy breakfast, getting enough sleep each night for the week before, exercising regularly and controlling stress) and preparing to deal with the time constraints of a standardized test.
If you need live help, a good tutor can provide one-on-one mentoring for the same price or less than a lot of group test preparation services. WyzAnt offers contacts to thousands of tutors all over the country that can help you perform at your very best for your test. It does not have to be a trial taking a standardized test if you plan ahead and get an edge.