Decide on the theme of your poem. Whether the lines of the poem are designed to convey a scene, tell a story or describe emotion, the underlying theme can provide fodder for your title. Write down your theme at the top of a piece of paper and brainstorm words and phrases that fit with that theme.
Decide on a structure of your poem. The poem's structure, in particular if it is a traditional verse, can form part of the title. For example, if you are writing a poem about Spring, you may choose to call it "Ode to Flowers." A love poem might have the title "Sonnet for a Summer Romance." Likewise, if you choose to write a free verse poem that uses complex analogies, you might use the title to give the readers a clue as to its hidden meaning. For example, a poem with images of empty spaces might be called "Loneliness."
Finish the poem before choosing a title. Although it is possible to write the title before any stanzas go on the page, you may find it more effective creatively to choose a poem title after the lines have been reworked and finalized. You may discover that your intention has shifted during the writing process. The title should reflect the content of the final poem.
Reread the poem and title a few days after you have written it. Putting the piece away and returning to it, will allow you to read the title with fresh eyes. This will allow you to better judge whether the title is interesting enough to keep the reader reading and whether it is the best possible addition to your poem.