You might want to review the Idioms chapter in the Manhattan GMAT Sentence Correction book. In addition, I recommend checking out the List of Common Idiomatic Expressions that appears in one of the Appendices of the PowerScore Sentence Correction Bible.

The Manhattan GMAT Sentence Correction book is available as a Kindle ebook for $9.99 at Amazon.com.

You can either buy the PowerScore book at Amazon.com, or if all you want is the appendix with the idiom list, you can preview the entire list using Amazon.com's "LOOK INSIDE!" preview feature. See https://www.amazon.com/PowerScore-GMAT-S ... tion+bible.

To a degree, however, I believe that the focus of the exam has shifted away from idioms a bit. Instead, there is now a greater emphasis on testing your ability to identify answers that present the intended meaning clearly, logically and concisely. This is in line with the GMAC's intent to test reasoning rather than memorization.

Nonetheless, I understand the impulse to study idioms in order to prepare as thoroughly as possible, especially if you've found that idioms are a weakness.

When you study idioms, I would use them in sentences and make note of any common incorrect uses, including any incorrect versions of the idiom that trap you in practice problems.

Good luck!