Try working through LearningExpress's Reasoning Skills Success in 20 Minutes a Day, taking it as a handbook on cracking multiple choice questions.
In a well-written test for grownups, it shouldn't be the case for most multiple choice questions that the answer is obvious on first glance. We're all used to this with math tests - one expects to have to do some calculation in order to determine the answer, no? But experience suggests that teacher tests go in less for choosing the right definition of a term than they do for applying the concept behind the term to derive a result. The correct answer choice is the one whose specifics and assumptions deviate least from the ones in the question stem. If the question stem describes what turns out to be a grade 7 student with inattentive-type ADHD, while answer choice b describes an intervention that is suited to a grade 2 student who's high functioning on the autism spectrum, some other answer choice is likely to be correct. It can be helpful to use the scratch paper to make assumptions visible and thus facilitate matching them up.