With unseen poetry you aren't expected to know the context so it is all about what you can see infront of you. First read the poem to see what it is talkimg about. Then look at the form of the poem, how it is set out, and see how it relates. Are the stanzas short or long, do they flow or are they broken? Finally always focus in on specific words and what the poet is trying to show you with these words, how we are supposed to feel when reading them, are they in the form of a methaphor or simile?
For an essay question I would set it out by the differnet points in the poem and then use the form and language of the poem to back uo each point I find.