Well, let's start with some diagnosis.
First, is English your primary language? This is important for how you will need to approach the whole Verbal arena. If English is your primary language, learn to relax and speak naturally in your writing. If English is not your primary language, then English is likely going to be counter-intuitive many times, and this will cause trouble.
Now, there are a lot of things about grammar and reading comprehension which would drive you crazy trying to remember them all, but there are a few basic rules of thumb:
* Generally, simpler is better. If you can't decide between two phrases to complete a sentence, the shorter one (if it still conveys the message) is usually the best choice.
* Essays get to the point fairly quickly. The writer will say most of what he means in the first and last sentences of the first paragraph. So, in reading comprehension, copy down the first and last sentence from the opening paragraph, and when you are in doubt, ask yourself which choice is in line with those statements.
* If a passage makes no sense, take a little more time and read it a bit at a time. Don't try to answer the question unless you are sure you know what is being asked, and what is the best answer.
* Just like the math questions, the earlier questions in Verbal matter more than later ones. Also, people tend to rush a bit, because all those words make people worry they will run out of time before they answer the whole section. You have more time than you may think!