I agree that getting the gist or mapping out the passage helps immensely.
While doing so some students contain this info in their heads and work from memory - not usually a good idea unless you have a photographic memory. Jot down some quick notes. This will help you with Main Idea/purpose, Style and Tone and Structure questions (and can even sometimes help you locate answers to detail questions!)
If you do the legwork/analysis check out answer choices and work backwards to see where the right answer choices come from. In most cases you will notice that the correct answer choice comes from the 1st two sentences of each paragraph. In a very long paragraph you may have to look at 3rd and/or last too especially if there is an opposition conjunction at the beginning of the sentence (opposition conjunctions are very important in any one of those sentences). Also pay attention to an opinion expressed (implicitly or explicitly).
Once you realize that almost all answer choices come from the first two sentences of each paragraph then you know how much to read. You will then need to be careful of traps etc. But the main thing is start to understand that such a mapping WILL save you time and effort and make you more precise (notetaking can save you time yes! You will simply not need to keep gravitating back and forth and relying on memory).
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