One of my favorite strategies to use with poems is an acronym TPDASTT. It's very useful for determining tone and theme.
Title--First you look at the title, before reading the poem, and write down any first impressions you may have.
Paraphrase--Go through the poem, not line by line, but by sentences--jot down the main, basic idea of each sentence.
Details: On the surface level--what is this poem about? Write down two-three basic things/subjects mentioned in the poem.
Attitude: Look at the poet's attitude toward the subject (look and see what you wrote down in the 'details' section above) he/she is writing about. How does he feel about it? This is the poet's TONE. I am including a link to a list full of really good TONE words.
Shifts: Does the poet's attitude change at all in the poem? I like to find specific phrases or words from the poem that go with the TONE.
Title: Re-examine the title, now that you have a deeper understanding of the poem. What do you believe the title refers to now?
Theme: What does the poem mean? What do the subjects in the poem represent, and what is the poet saying about them through his TONE?
TPDASTT is also known as TPCASTT (where the C stands for connotation), but I prefer the added 'details' aspect for a more literal reading early on in the steps.