Read. Take a practice test. Any test prep book should come with several tests. Read.
When I say read, I don’t mean read a test prep book, I don’t mean read lists of vocabulary or formulas. Read everything you can find. It doesn’t have to be great literature or even non-fiction. Science fiction, historical fiction, fantasy, it doesn’t matter. Reading adds depth to your writing. It expands your vocabulary. It also helps you find your voice.
However, that’s not advice that is relevant immediately before, or even a few months before a test.
What test prep institutes do is teach a few strategies, including some basic knowledge of statistics and the structure of the tests. This is very useful, but all that information is available in any of a hundred books or even online. If you can’t bring yourself to study, and I certainly have my own procrastination problems, then a test prep institute may be helpful.
There are several problems with what test prep institutes do.
First of all, they’re interested in your score, only your score and nothing else. Your core understanding is irrelevant to them, but it should be relevant to you. We take these tests to get into places where we’re going to need the knowledge that the tests are supposed to evaluate, so lacking the knowledge is a bad idea in the long run.
Second, test prep institutes do what works for the majority. You are the only person who really knows how your mind works and what will help you succeed. Do you learn better from visual or auditory stimuli?
Finally, remember to take all advertising with a grain of salt. People generally do significantly better the second time they take the exam, so stating that students gain an average of fifty or a hundred points, isn’t really that relevant. Also, when looking at average scores for their students, consider who their students are likely to be. Test prep institutes attract people who are overachievers, for obvious reasons.
Test prep institutes can be a useful tool, but you’re probably better off studying on your own, or with friends and family. That’s what test prep institutes don’t want you to know.