How do I begin to analyse an unseen poem?

The biggest question to ask yourself when analysing a new poem is 'why?' - why does the writer use those specific words or that literary device? What effect does that have? It is easy to spot that a poet uses alliteration, but it is much more interesting to see why they use it. For example, if a poet describes a character as having 'silky, serpentine speech' then they are using alliteration and sibilance to evoke the 'sssss' sound of a snake, perhaps implying that the character is not trustworthy.You can look for different structures or devices in the text to help guide this, such as rhyme, rhythm and form. A sonnet is traditionally a love poem, so why might the poet have written a sonnet about World War One? The structures and devices are often related to the theme, so by isolating the poem's themes you can begin to dissect how the devices work either to promote that theme or to work against it.Examples:A poem that uses a lot of long vowel sounds (oh, ah, oo) that is about somebody crying and moaningA poem with a very strict rhyme scheme and rhythm that talks about a clock ticking and time passing