Hi cg123,
To increase your verbal score to a higher level, you have to go through GMAT verbal carefully to find your exact weaknesses, fill gaps in your knowledge, and strengthen your skills. The overall process will be to find weaker areas, learn all about how to answer questions of types that you aren't that comfortable with now, and do dozens of practice questions category by category, basically driving your score up point by point.
For example, assume you begin studying Critical Reasoning. Your first goal is to master the individual Critical Reasoning topics: Strengthen the Argument, Weaken the Argument, Resolve the Paradox, etc. As you go through the questions, do a thorough analysis of each question that you don't get correct. If you missed a Weaken question, ask yourself why you didn't get it right. Did you make a careless mistake? Did you not recognize what the question was asking? Did you skip over a key detail in an answer choice? Getting GMAT verbal questions right is a matter of what you know, what you see, and what you do. So, any time that you don't get one right, you can seek to identify what you would have had to know in order to get the right answer, what you had to see that you didn't see, and what you could have done differently to arrive at the correct answer.
Also, check out the following article:
How to Score High on GMAT Verbal on the Focus Edition