What poetic devices to look for when analysing a poem?

Here is a list of some of the main elements to look for when analysing a poem - not every poem will have these, and most of all these elements should be considered in the context of the poem's meaning, discussing the effect of each device. 

Structure - shape of the poem, significance of the title, whether it has stanzas, a refrain, a rhyme scheme, meter, a known form (sonnet, extract from an epic...), which words/parts of the poem stand out, which parts are linked to one another

Narrative voice - first/third person, tone, who the narrator is addressing, whether/how the reader empathises with them, emotive language, direct/indirect speech

Language - sibillance, alliteration, assonance, juxtaposition, oxymoron, conjunctions, repetition, active or passive verbs, register (vernacular or 'raised' diction), tenses, punctuation, long or short sentences : how themes/ideas are explored, interlinked or contrasted

Imagery - semantic field, metaphors, comparisons, simile, conceits, symbolism, allegory, personification: likening an object, person, feeling or thought to another, to either highlight a similarity or emphasise a particular aspect by presenting it in a new way

There are plenty more devices to look into, but those cited above are a good start to make sure you get the most out of your experience of the poem!