Hi here's some advice about each of the sections.

RC
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Read articles everyday from different magazines such as mckinseyquarterly or scientific american. Those articles normally come with some headlines that sum up the content. Try to read the article without reading those headlines, as you would read a GMAT passage, taking notes, scope of the passage, main idea, purpose and so on. Check your notes with the headlines.

You should be aware of the typical traps for each kind of question and categorize them when you find them.


CR
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I think the best book is Critical Reasoning bible. I find very useful modeling and taking notes on CR. Again be aware of the traps and patterns to solve each type of question.


SC
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If you don't have it, get MGMAT SC. Practice as many problems as possible FROM OFFICIAL RESOURCES specially GMATPrep.

Look for explanations by experts such as Ron Purewal or Stuart and take notes from their comments on the questions.

Good luck

Thank you so much mikeCoolBoy! I already have SC MGMAT and I will by Critical Reasoning Bible.