You can discover a lot about a poem by comparing it to one by another author that deals with a similar subject. You could compare features such as theme, form, structure, rhythm, language and figures of speech.
The key thing to do when comparing poems is to note the points where they are similar and the points where they differ. You could make a list noting similarities and differences between the two poems.
Comparison of 'Neutral Tones' by Thomas Hardy and 'She Walks In Beauty' by Lord Byron
Both poems have a speaker who draws attention on a central unidentified figure.
This unidentified figure in both poems has had a deep effect on the speaker (even if this seems to be being denied in the Hardy poem).
Both poems reflect on a significant moment in the speaker’s life.
Both poems make use of imagery to convey the speaker’s feelings towards the unidentified figure.
The speaker in Hardy’s poem looks back at a love that has died, whereas Byron’s poem concentrates on an attraction that has only just begun.
Hardy’s poem sets out to downplay the effect the person has on them. Byron’s poem fully acknowledges and expresses that effect.
Neutral Tones focuses on a memory of something in the past; She Walks In Beauty is about a more recent and immediate encounter
The poems are different in tone. The title of Hardy’s claims it is neutral but there is a distinct air of regret about it. Byron’s poem is mostly positive and celebratory.