One thing that helps in a multiple choice exam and helped me get 100% first try in ATPL flight planning was taking a second to read the question and think about what the answer should be.
Use this information to immediately strike out 1, 2 or even 3 of the answers.
For example (and I was stunned when this happened), my PNR question in the exam had a decent headwind and of the 4(?) answer choices, only one was past the nil-wind PNR quoted (bear with me in case i've remembered this wrong - PNR moves into wind right?). Anyway, whichever, the point was that 1 of the 2 hardest/highest mark questions had only one possible answer. I therefore did no calculations on that one, picked the only possible answer, and moved on (had some time to spare at the end and came and checked it but there was no pressure because I was already sure I had the answer).
(the other thing that helped me get 100% first time was the Lionel's old course at Moorabbin - suspect he's not around any more?). For this more than any other, a face-to-face course is a worthwhile investment.
UTR