First, they provide structure. If you're diligent about taking these tests at regular intervals, such as once a week, you'll get yourself into a good study rhythm, and lock in 2 or 3 hours of regimented practice in addition to your regular studying. Second, these tests give you a good assessment of how you're progressing. There's no guarantee how you'll do on any given test—and this is true for the actual test as well as practice tests. But what you can do is use these practice tests to establish a score range, a general assessment of how well you're doing. If you take enough of these, and you're putting the work in, you should start to see an upward trajectory in your scores. Once you start to hit your target scores consistently, you'll know that you're fully capable of hitting those scores on test day.
That depends on you, of course, your schedule, and how long you've got until the test (you'll find some good approaches here from BrightLink Prep). As a rule of thumb, though, it's always good to begin any program of study—whether it's self-study or with a tutor—with an initial practice test. Even if you've never seen the material before, this will give you a starting point. If you're studying on your own, you'll familiarize yourself with the test, and get a handle on what you need to focus on. If you're working with someone, use that first test to help the tutor work with you on a study plan. After that first test, aim for one full test a week, if you can, with one final test a few days before the real one. You don't want to cram too much in in that last week, and if you have an off-day on a practice test, you don't want that to carry over with you into the real one. Remember, as you're practicing, don't skip or pick and choose sections—take the whole thing. By committing to a full test, even in practice, you'll condition yourself for the 3+ hour marathon you'll be facing on test day, and make it much less daunting. Similarly, you'll want to try to simulate the test environment during your practice tests—that means no phones (even on your desk or table!), no distractions—and keep to the allotted time!
Tests are easy to find—here are two great resources for some good paper and computer-based ones: one from Prepscholar and this one from CrunchPrep. And keep in mind that each company, whether Kaplan, ETS, Manhattan, whichever—sometimes have slightly different styles to their practice tests that may influence your scores slightly.
None of this requires an overly large time commitment—just a few hours a week (in addition to your regular studying, of course!) to make sure you've got a structured framework, and progress that you can easily measure. And once you've gotten a feel for these practice tests, you'll be ready for anything they might throw at you on Test Day!
About the Author
Steve Markofsky is one of our most experienced and qualified test prep tutors. For more information on GRE tutoring and to see profiles of tutors like Steve, click here.