Without a thorough knowledge of the words that you'll find on the GRE, you won't be able to do well on the verbal section. Look for lists of common GRE vocabulary words—you can find these online or in study guides—and work toward memorizing them. You can also study word anatomy—roots, prefixes and suffixes—so that you may be able to guess the meanings of words that you don't know.
A profession GRE tutor can help you to learn techniques for taking the GRE, which can improve your verbal score. In fact, some tutoring companies offer a guarantee that you'll improve your score after taking the course. You can get one-on-one or group tutoring with a well-known company, or you can hire a private tutor.
A study guide will help familiarize you with the components of the test and help you to figure out strategies for taking the verbal section. A good study guide should include practice questions, explanations of the answers and lists of vocabulary words that you may find on the exam.
Taking practice exams will give you hands-on experience taking the exam, which can help you feel more comfortable when you take the real GRE. Look for former GRE exams directly from the GRE creator instead of exams that are meant to simulate the GRE. This is a more accurate way to practice the test. Get comfortable with the format of the test and the instructions for each part of the test.