The best advice I can give is to read the question very, very, VERY carefully. Then read it again. Often the difference between a correct answer and a wrong one will be one word in the question. For example, does it use the word "height" or "altitude". That was the difference in one of the questions in my IREX exam. I found it only in reviewing my answers before the time expired.
Another question a friend had was a real prick. It gave an ETA and a day for arrival YSSY and a huge sheet of weather information. It also stipulated that the nearest alternate was 45 minutes away and asked how much extra fuel was required. The options were 0, 15, 30 and 45 minutes. After working all the weather information the conclusion was that the TEMPO and INTER did not apply and that no alternate was required. Obviously 0 minutes was the answer. WRONG. Look at the ERSA and on a week day at that time 15 minutes holding fuel was required.
Read the question very, very carefully.
