How to fix GMAT from coming in below practice scores

Each year, eager b-school hopefuls line up to take the GMAT, and each year many end up with a score below what they had been getting on their practice exams. What went wrong? Why the discrepancy? The answer is never easy to ascertain, but there are several questions you can ask yourself to try and figure out what happened. One of the most important ones is actually rather simple: did you practice for the test environment as well as for the questions themselves?
Since the GMAT went to a Computer Adapted Test (CAT) format, it has become increasingly difficult to practice in an environment that exactly simulates the actual test conditions. In the old days, when the test was simple paper and pencil, you could sit in a quiet place, take the practice exam, and feel essentially like you do in the real thing. Now, with all the security and isolation, not to mention staring at a harshly glowing CRT screen for 3 ½ hours, the actual GMAT test makes for a very difficult environment to duplicate at home. Given this dilemma, we always recommend applicants try to simulate the actual test conditions as best they can.
For starters, when taking a practice test, make sure you take it from start to finish. Unlike training for a marathon, where you rarely run the full 26 miles until race day, for the GMAT, you want to be building your stamina by taking complete practice tests from start to finish. Don't do this until you have studied and prepared, but after completing an instructor-led class for example, you should begin taking practice tests as your testing date draws near. Know that stress will add to your fatigue on test day, so if you haven't acclimated to the three hour marathon, you won't perform well.
Secondly, make sure you are taking a computerized test. It's fine to work individual problems from a book as part of a well-balanced training regimen of course, but when taking an actual practice exam, make sure you do it on a computer, just like you will have to do on the real thing. There's nothing like simulating the stress of the real test with a running, onscreen clock just like the real thing. And no lying back on your sofa in your pajamas either! Get dressed, sit up, and click through the test just as you will do on exam day. This can also help prepare the brain for the correct environment.
One final tip is to take the practice tests at the same time of day as your actual testing appointment. The brain works in mysterious ways, and biorhythms are a reality. Make sure you are working out your brain in sync with your circadian rhythms by sitting for your practice tests during a similar time window as your actual test.
If you prepare for the GMAT by approximating the actual test environment, you will build confidence and prepare your mind to function at peak levels when the date arrives. Good luck!