If you ask 10 people, they will tell you 10 different strategies like do this, do that etc. But the easiest strategy is to 1st read the question paper and select the questions which you would like to answer and mark them serially according to your level of confidence with each question.
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For example: if you can answer question no. 3 at your level best, then do it first because as they say 1st impression counts and stike the rod (i.e. strike the mind of the examiner with your knowledge) and follow others as mentioned above.
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This way you will know which ones to answer, how many answered and how many left to do because sometimes out of anxiety students make silly mistakes in answering total number of questions.
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and no matter how many strategy you follow and prepare, it all depends on your level of preparation and knowledge.