Our approach to idioms - especially if you are a non-native speaker - is to downplay their importance. There is little point spending energy trying to memorize idioms, as the list is theoretically endless.
With a few exceptions of idioms we see recurring frequently, we encourage students to relax about idioms and follow these guidelines: first eliminate whatever you can by finding grammatical mistakes, and answer choices that are illogical. Next look for wordiness and awkwardness and eliminate stylistically flawed constructions. After eliminating the former types of mistakes If you see two variant answer choices that have no grammatical mistakes, are logical, and are concise, but which are only different because of the alternation of a preposition - you can hazard a guess, and go with your gut. While you may lose the point if your guess was off, you have still considerably increased your chances at guessing correctly.