On test day, you will be allowed to bring snacks that you can leave in a locker in the test center. I would definitely recommend doing this. Try to bring something healthy, which is more likely to give you energy. If you usually study with caffeine then bring your usual drink to the exam. If you don’t usually drink a lot of caffeine, today would not be a good day to start. It is more likely to throw you off and make you unnecessarily nervous than give you an extra boost of energy.
You will also have the option of taking the full 8 minutes for the break or starting the next section early. I would recommend taking the full 8 minutes. Even if you feel like you are ready to move on early, and are tempted to get the test over with early, you are likely to do much better if you give your mind as much time as possible to relax.
Once you have finished the test, you will be able to see your unofficial score, which includes everything but the AWA section. You will then have two minutes to decide whether or not you want to cancel. Even if you decide to cancel, you can reinstate them for a $100 dollar fee within 60 days. This feature was added in 2014. Previously test takes had two minutes to decide if they wanted to report or cancel their scores. However, they could not look at their scores, so they just had to judge based on how well they thought they did. If you are new to the GMAT, you have been given a gift, don’t waste it! Make sure you take full advantage of this opportunity by doing your research and deciding before the test what score you will accept. That way you will know immediately when looking at it if you want to keep it or not.