I'm assuming you've gone through the best Verbal materials: MGMAT SC, OG Verbal, Powerscore CR, etc.
GENERAL TIPS:
Beef up the grammar skills. You can ignore most of the challenging vocabulary on sentence corrections as long as you identify what part of speech each word is, and how it functions within the sentence. To do this, you'll need to spend some time with a solid English grammar review book. I recommend pairing a heavy-duty review book, like the Oxford Guide or those published by McGraw-Hill or Longman, with a "fun" book like Writer's Express or English Grammar for Dummies.
Read and listen to high-quality English publications. My recommendations include The New Yorker, the Atlantic Monthly, the New York Times, the Wall Street Journal, or any scholarly journal that you find interesting. Listen to NPR or audio books of English-language classics. Set a regular schedule for your reading and stick to it. Even twenty minutes a day will help you conquer Reading Comprehension.
Make a vocab journal. Write down any words you don't know as you encounter them. You'll start to notice that certain words appear over and over again. Make flashcards for the ones that have tricky definitions or mean the opposite of what you'd expect. Think like a thesaurus. It is much easier to memorize synonyms for words than their full definitions. Start grouping words together mentally (and on paper) according to their meaning. For example, words like "pusillanimous," "poltroonish," and "timorous" would go on the "shy" list.
Seek out Advanced CR for harder vocab words. Once you've practiced identifying the conclusion, evidence, and assumptions and are confident with the Critical Reasoning question types on the GMAT, consider buying an LSAT practice guide like the LSAT LR Bible. The LSAT has significantly more challenging CR questions and the format is the same as those found on the GMAT. Don't neglect your GMAT practice, but if you can master the LSAT CR, then the GMAT questions will start to feel easier.
Go more slowly with Word Problems. Practice translating these questions from English keywords to Math equations. Be patient at first - these questions may be especially frustrating vocab-wise. Luckily, the common phrases such as "less than," "is the same as," and "product of" are easily memorized.
CRITICAL REASONING TIPS
Identify the Conclusion, Evidence & Assumption(s). This should be your first step for all of the Critical Reasoning question types. The conclusion and the evidence will be explicitly stated in the passage, while the assumptions will require you to sit and consider the author's point of view. What needs to be true in order for the conclusion to be correct based on the given evidence?
Find the purpose of each sentence. Sometimes CR questions will ask what the function is of a part of the argument. You may see questions that ask "which role" a sentence plays. Try to place it into one category: conclusion ,or evidence? If the sentence was removed from the paragraph, what would be lacking?
Know the overall flow. Arguments have a tendency to follow one of two shapes: a triangle or an inverted triangle. Does the author start by making a specific conclusion and then provide more general evidence, or does he begin with observations and then get to a thesis? Use variables to describe the structure. "Y leads to X which leads to Z" is different from "Y turns into Z unless Y is prevented." Be on the lookout for "If X, then Y" relationship.
Paraphrase the argument. Dumb down the complexity of the argument as you read, as if you were explaining it to a child. You may want to write down a few short notes to help you. The idea is to ignore the petty details and see through to the author's main point and to the evidence he provides to support his point.
Choose a verb. Questions about argument structure often ask about the "methods" an author uses. You already know the flow of the overall argument, now give it an overall purpose and label as an infinitive verb. Common verbs:
to explain
to dismiss
to theorize
to strengthen
to demonstrate
to revise
to assert
to suggest
to interpret
to reconcile
to challenge
to predict
Look for transitions. Transition words and phrases are like signposts pointing your way through the logic of the argument. They tell you what is coming next. "Specifically..." means a more detailed example will follow. "Thus," means a summation is to be expected. "While this may be true..." is a phrase that shows a concession is about to be made. Keep a study sheet of transition words and divide them into categories: Examples, Adding, Contrasting, Emphasis, Resulting In, etc. It's an ongoing process to familiarize yourself with these, but a worthwhile one.
Determine what is missing for Complete the Passage Questions. What does the blank represent? Often it will be either a restatement of the conclusion, or another supporting piece of evidence, but it could also be an action advocating by the author, or an example of the author's argument applied to the real world.
Make a prediction (and write it down)! This is the most important strategy for CR. You've got to trust that you understand the argument enough to know what should be the correct answer. Don't worry about making it perfect - just get something down on paper! If you think of your prediction but don't write it down, you risk forgetting it or twisting it to fit the answer choices.
Eliminate out-of-scope answers. While the correct answer may not perfectly match your prediction, the simple fact that you took the time to think critically while you came up with a prediction will help you understand the author's focus and the flow of his argument. Eliminate answer choices that would NOT follow the gist of the paragraph. Especially look for those that are outside the scope of the author's focus, a favorite CR wrong answer type!
Try the Negation Technique. An assumption is something that needs to be true and is required in order for the Evidence to lead to the Conclusion. If we negate the answer choices then the correct choice will weaken the argument the most. This is an excellent strategy to try for Assumption questions.
Good luck with your studies! A little hard work, and you can definitely bring up your score 40-70 points!
