Once you have completed the exam, go back over your answers to make sure you answered all the questions. The exam software should alert you to unanswered questions. If you have no idea what the question is asking, answer anyway. Even if flipping a coin, you will have a 25% chance of being correct. After you make sure all the questions have answers, then review your answers.

As you review, be careful of changing your answers. There are conflicting thoughts from experts as to whether you should change an answer or not. After working with thousands of students taking exams, I can tell you that in my experience, people will often change an answer to an incorrect response.
Rather than lose points by changing answers, use this process. When reviewing questions, change an answer only if you remember new information. Here is how it works: as you work through the exam, you may remember something that will help answer a previous question. If you remembered something new that you did not consider previously, then it is appropriate to change an answer. Do not change an answer because it looks wrong.
Often students will tell me that they changed an answer because it looked wrong. Or because they were worried that they chose too many letter “b” responses. This is not a solid logic. Your initial reaction, even if you were guessing, is usually the best response. A keyword or phrase can help you remember something that you did not previously consider.
“Looks wrong” is not a strategy. When reviewing your answers, ask yourself whether you found new information before changing the answer. If the answer is “yes,” then change the answer. If the answer is “no,” then go with your initial response. Using this strategy will help you to decrease the number of times you change the correct answer to an incorrect answer.