Purchase a GRE study guide. Some of the prominent publishers that produce helpful study guides for GRE preparation include Kaplan, Princeton Review and Educational Testing Services. These books can be purchased from a local book retailer or ordered on the Internet. You can save some money by ordering a used copy of the book. Find a copy of the book, new or used, that comes with a CD-ROM study aid. This software usually contains practice tests that are meant to mimic the actual GRE exam. You can purchase multiple books, but if you are short on time, one book should suffice. The most important part of the book, for vocabulary purposes, is the list of most commonly used GRE vocabulary words. Each of the major publishers will have similar, if not identical, lists of these words.
Create vocabulary flashcards using standard note cards. You can purchase note cards at any major retailer that carries school supplies and stationary. Focus first on the words provided in the "most used" vocabulary list. Write the word on one side of the card and the part of speech and definition on the other. Place your cards in a plastic note card file case and carry it with you everywhere you go. Use every moment of your free time to go through a few cards and learn the definitions.
Practice using the words in sentences regularly. An article published on the Michigan State University website notes that rote memorization will likely be insufficient for improving your score by itself. Instead, it is necessary to learn how the words are used and not just the definitions.
Read consistently. You can improve your GRE score by understanding the basic nature of the English language and how words function within their context. The Michigan State University website also suggests reading progressively more difficult literary works to improve your language abilities. Take note of new and challenging vocabulary words as you read and add them to your note card list. As you add the words, also add the sentence or context in which you found them so that you will have a strong understanding of how to properly use the words.