Hi fighting750.
The GMAT doesn't use a lot of advanced vocabulary. So, your best move may be just to make a list of important words that you commonly encounter when answering GMAT questions, such as
invalid,
premise,
attribute, and
warranted, and study those words.
Also, you can improve your ability to read the type of writing that appears on the GMAT by reading articles from the following publications regularly.
• Smithsonian
• BBC History
• Life Magazine
• Economist
• The New York Times
• New Yorker
• Archaeology Magazine
• Science Magazine
• Scientific American
• Science Daily
• Astronomy Magazine
• American Scientist
• Atlantic Monthly
• Physics Today
• Wall Street Journal
• Harvard Business Review
• Harvard Magazine