FAQ:How much can I really improve my score by browsing through a word list?

From GREdic wiki, the free GRE test preparation resource

Spending a lot of time goint through a word list can boost your score tremendeously. If you combine that with occasional quizzes, practice tests, and if you try to use the words you learned recently in practice, you're on the right track to storm the verbal part of the GRE.