How would I approach an unseen poetry question?

Tackling an unseen text, especially a poem, may seem daunting at first. However, the more you practice - the more comfortable you will become with close critical analysis, and you may soon even find it enjoyable. Firstly, start with simply reading the poem at your own pace. Don't think about techniques, just focus on absorbing the poem. It might remind you of a movie you've seen recently, or a past memory - hold on to that! Poetry is written by people so focus on any initial reactions you may get from the poem. Then, read the poem again, picking up on the poem's general themes - the most reoccurring ones being love, sex, death and family. Understanding the themes will help you understand the poem and its message (or lack of). It is advisable to outline your central themes in your introduction in order provide structure for the rest of the essay.
Once you've figured out what the themes are, then you can use the body of your essay to trace the ways in which the formal elements of the text advance these themes. These elements cover form, structure and language. In my close readings, I tend to break these down into six specific techniques: stanza form, sentence structure, imagery / recurring motifs, diction, rhyme and metre. Mentioning how the poet uses each technique, or fails to use it, ensures that you are covering as much ground as you can, in order to provide a cohesive evaluation of the poem's concepts and message. Use highlighters to underline certain words, rhymes, or images that stand out to you. Put yourself in the poet's shoes and reflect on why they chose to structure their poem in the way that they did. This may help make the poem more accessible and understandable.
My final piece of advice is to remain calm and trust yourself. The beauty of close reading is that as long as you back up your interpretation with effective structural and language analysis, your argument holds water.