The best way to prepare for this sort of exam is by learning techniques which commonly feature within poetry. Once you have learnt these, practise applying these techniques to poems you haven't seen before, and try to spot patterns or recurrences. The best thing to do is try and include a comment on the following things: 1. The structure - i.e. rhyme scheme, juxtaposition 2. Grammar - i.e. imperatives, demonstratives 3. Sounds - i.e. alliteration, onomatopoeia 4. Metaphors/Similes As long as you try to include something from each of those areas, then you have everything covered!