The EA exam is very different and very difficult compared to other exams you have taken. Because of the large volume of tested topics, you have to adjust to answering questions that appear very difficult and require educated guessing.
If you do not know the answer to a question, guess, but make an educated guess. First, rule out answers that you feel are incorrect. Second, speculate on what the IRS is looking for and/or the rationale behind the question. This may lead you to the correct answer. Third, select the best answer, or guess between equally appealing answers. Unless you made an obvious mistake or computational error, try to avoid changing your answers. Your first guess is usually the most intuitive. If you cannot make an educated guess, read the question and each answer and pick the best or most intuitive answer.