Consider an Energy Boost - diet soda, caffeine pill, coffee, Red Bull etc. If you normally have a can of Diet Coke or a coffee to perk you up in the morning you'll definitely want to honor that ritual Day Of. The big caveat here is to test out your chosen booster with a practice run. When I took the Physics GRE last month I did exactly that, using the 5-hour Energy drink. The Saturday before my test I did a complete dry run: getting up at an ungodly hour, eating a solid breakfast, walking to my test center, downing a 5-hour Energy, taking a timed practice exam in an empty room. I found two things, 1) I performed significantly better than on my previous four practice exams, 2) I couldn't make it through the test without a bathroom break. So I adjusted for the Day Of by drinking my booster earlier in the morning and taking two bathroom trips at the test center before the test began. No score report yet, but it definitely seemed to help.
Edit 1/7/2011: Yep, got my score report - 60 points higher than my best practice!
On a related note, Eat a Hearty Breakfast. Don't eat a 2000-calorie meal. Don't eat foods that your body isn't used to. Do eat a small, dense meal with some fruit, fiber and protein. An ideal example is a bowl of cornflakes with walnuts and sliced banana. Make sure you're hydrated as well. This doesn't mean shotgunning a bottle of water right before starting your test, but drink some water early in the morning and during all of your testing breaks. For SAT and GRE you'll get at least one break long enough to eat a quick snack and use the bathroom - Use your Breaks! Even if you don't feel like you need to go to the bathroom, give it the old college try. It'll be good to stretch your legs and might save you some bladder discomfort later in the test. Even if you don't feel hungry, nibble something high in protein like trail mix or peanut butter crackers.
You will also want to Dress in Comfortable Layers. You can't change the thermostat in your test center, and thanks to the wonders of modern climate control your room could be unpleasantly frigid or sweltering no matter the time of year. Be prepared by dressing in a few comfortable layers - for example, t-shirt, long-sleeve shirt, then hooded sweatshirt. Be thankful that you're not taking the MCAT (for medical school admission) where your score is voided if you remove layers of clothing during the test! No joke, this happened to a friend of a friend.
Wouldn't it be a shame if after all your careful planning and hard work you forgot to Bring All Necessary Items to the test center? Something as stupid as not having a sharp pencil shouldn't stand between you and your school of choice. All the required and recommended accessories for the SAT can be found on the official College Board website, while those of the GRE can be found at the official ETS website. Make sure your photo ID is not expired and your pencils are no. 2!
With any high-stakes and high-pressure test will come some gut-churning anxiety. If the night before your test you feel more inclined to toss and turn or cry hysterically than to sleep peacefully don't worry, you're not alone. The key is to Build Up a Sleep Buffer by being extremely well rested for the three or so days leading up to the test. Don't try to pull an all-nighter or put in a 12 hr. study session a few days before the test, instead do something active that will give your mind a rest and tire our your body for bedtime.
In later posts we'll talk about what happens before test day with some tips on prepping for your test. You can also check out our advice if are asking yourself "when should I take the GRE?" But for now congratulations on being in top form Day Of. You may start your tests...