GMAT Study Guide - a prep wikibook
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The only teaching guide that I (User:Nervousgmat) found useful was a Manhattan GMAT guide. I reread it at least three times and referred to it when I couldn’t explain why the right answer choice is in fact correct. MGMAT SC guide = Bible for SC. For practice I did all of the OG11 guide and the OG verbal workbook. Make sure you create an error log of all the SCs you got wrong and come back to them in a month or so. I guarantee that you will make the same mistakes again. Make sure you understand the correct answer. If you still don’t know why a certain answer choice is right, search the forums or post your question. A lot of times you will learn a piece of information that you never knew before. Idioms are important. Learn as many as you can! I am attaching an example of the idioms file that I found on the net below.
Once you learned the concepts, focus on strategy, such as 2/3 splits, scanning the choices for an error tested, etc. I can’t emphasize enough that one should learn the concepts first and then learn the tricks. Knowing only the tricks will not get you far. GMAT questions are designed to fool you, so learn your basics first. Then practice, practice, and practice again! There is tons of material out there. Try 1000 SCs and the brutal SCs (see this link for Brutal SCs).