Most students open a past paper, start at question one and work until they run out of time. That tests stamina more than understanding. An examiner reads the same paper differently: as a plan for where the marks are, and where they are hard to earn.
Start with the marks, not the questions
Before answering anything, go down the margin and add up the marks per topic. A paper that gives twenty marks to one chapter is telling you what the syllabus writers think matters. Do this for three or four years of the same subject and the same chapters keep coming back.
Read the verbs
State, describe, explain, compare and evaluate ask for different amounts of thinking. A question that says explain wants a reason, not a definition. Circle the command word first, then underline what it is being applied to.
A mark scheme is the examiner's honest answer to one question: what did you actually want to see?
Mark yourself, then mark the gap
After attempting a paper, mark it against the scheme, then write down why each lost mark was lost: a fact you did not know, a step you skipped, or a question you misread. The third kind is the cheapest to fix, and it is usually the biggest.