Study the works of poets you admire to see how they have titled their pieces. Do the titles parallel the poem itself or do they contain an element of differentiation? The point is to find inspiration and ideas, not to replicate those already written.
Review the works of songwriters or singers who most closely parallel poets for title ideas. Choose someone whose work most closely resembles your own poetry style.
Avoid one-word titles, which are too broad for most works, including poems. The themes of love and regret have been the genesis of thousands of poems (and songs), but using these words as titles will probably instill a sense of disappointment in your readers, who will expect something more insightful.
Avoid wordy, slightly technical titles. Remember that you are not writing a how-to article or a service piece designed to convey specific information. Also, wordy titles in poetry can be a sign that those words should be contained in the poem, not the title.
Repeat in the title any key phrases or verses in your poem. Chances are, if the words were important enough to repeat in the poem, they may set the right tone for the title, too.
Capture the emotion of the poem in a few pithy words. Think about what inspired you to write the poem in the first place.
Invoke an image or ideal that captures the essence of your poem and translate those images to words for your title.
Seize upon a theme, either expressed or implicit, in your poem. In other words, your title may contain words that are not present in your poem. In this way, you are signaling to readers that they find meaning in the title as well as the words that follow.
Stay true to the tone of your poem with the title. Invoking irreverent or sarcastic humor in the title of a poem that teems with sentimentality will probably create confusion and consternation in your readers.