When reading a poem closely to interpret its meaning and nuances, what can give you clues about the theme of the poem?

The meaning behind unfamiliar words 
Breaking it down into sections; such as changes within the poem
Diction's- What are the most significant words and what do they indicate 
Look for words that indicate feeling 
Words of 'I' 'We' 'Us' 'Them' and etc. Can be used to determine if it's meant to be the poets Point of view, such as if it's a narrative or description or so
Literary Devices- Is it a metaphor is it a paradox. Do they repeat words for significance (Alliteration).  
There is so much more but this is what i can think of on the top of my head