When you are doing a critical appreciation of a poem, you don't need to worry about data. However, there are a number of aspects of the poem that you need to consider in detail.
For example, the first step you should take is to look at the structure of the poem. This includes the stanzas and the rhyme scheme, if any.
Secondly, you need to consider where the poem is set—both time and place—as well as any speakers or characters in the poem.
Next, you will want to take a close look at the kind of language that the author uses. Remember that language includes stylistic devices, like imagery, metaphors, personification, and alliteration. Note any relevant examples and start thinking about the purpose of these devices. If you need help with these devices, check out the reference link provided.
Then, you will need to work out the author's message and any themes which are present in the text.
Finally, you want to put all of these pieces together. Consider how the author uses structure, language, and themes to emphasize the poem's message. Remember to support any arguments with relevant examples from the text.