You'll do better on a test if you're healthy and alert. Get a good night's sleep the night before. Consider going to bed early for a few days before the test so that you're able to fall asleep the night before. If you're hungry, you'll be distracted, so start the day with a filling breakfast and bring along a healthy lunch and snack to fuel your body. The GED lasts seven and a half hours, and you'll be given plenty of breaks including time to eat lunch.
The day before the test, write a few notes about the areas that are most difficult for you. For example, if math is a weak point, you should jot down some of the formulas that you tend to forget or confuse. If social studies is your weak spot, write down some important dates or concepts. You won't be able to use this "cheat sheet" during the test, but you can take it out to review just before you take that section so that the information is fresh in your mind.
Get to the center early so that you can register and get comfortable before the test starts. This also allows you to have some time to review notes before you take the test. You'll need a photo ID and pencils to take the test. Pack these items the night before so that you're sure not to forget them. Wearing a watch can help you keep track of time if you happen to be sitting in a desk where you cannot see the clock. You will not be allowed to keep your cell phone with you.
The GED primarily contains multiple-choice questions. You do not need to know the correct answer to get it right; if you're unsure, eliminate the answers that you know are wrong, then guess from the remaining answers. Skip any questions that are too difficult for you, then come back to them after you've finished all the others. On the GED, your score is determined by how many questions you get right. You are not penalized for a wrong answer, so it's better to guess than to leave an answer blank.