Pick two poems dealing with the same theme. Establish this theme as your subject; relate your points to establish continuity. Be specific in the areas you compare and contrast.
Choose the form of the poem you are analyzing. You might select poems based on theme, or on techniques such as metaphor and rhyme. Concentrate on poetic techniques if a thematic link is not obvious.
Give a balanced comparison that include contrasts and similarities. Observe the differences in the two works, and give an equal account for each.
Organize your essay text-against-text. You might organize the essay according to how the theme is handled in the two poems. Group your points in blocks.