As you go along put check marks next to questions you're not sure of so you can quickly go back to them as time expires. Your answer might be correct or you might receive partial credit. With essay exams say as much as you can, but use short paragraphs and write legibly. Answers often pop up in other questions. Keep that in mind.
First impressions are often best.
When in doubt go with your initial response. When a question is difficult to visualize draw it out. Assume a possible answer, then work backwards to see if you are right. Eliminate all possible wrong answers first then make an educated guess. Sit in front of the class.