As with any exam task, you should balance using your own ideas to engage critically with the text with, maintaining a strong focus on the requirements of the question. Before you start, ensure that you have an excellent range of subject terminology to hand, and then let your critical approach be guided by the assessment objectives for that exam section. On unseen poetry questions, most exam papers assess your analysis of language, structure and form.
Read the poem twice. During your first reading, identify the message, key themes, the speaker and subject of the poem. On your second read, look closely at language, poetic and structural techniques such as extended metaphors, alliteration, description, enjambment and rhyme schemes (or lack thereof). Annotate the poem by highlighting key lines or writing notes along the sides. When you identify language, form and structural techniques and patterns, always link them directly to the wider meaning or mood that the writer is trying to create. Finally, think about the effect that these features have on the reader.