Research lyrical poem forms. Form choices include the traditional 14-line sonnet (each line containing 10 syllables), the ballade (three sections of verse with eight lines apiece), and the villanelle (19 lines long).
Pound out a rhythm. Once you've settled on a rhythm, you can identify the meter of the poem. Sonnets are written in iambic pentameter, and its rhyme scheme is abab-cdcd-efef-gg, with each letter representing a different rhyming sound. Anapestic meter is another option. An example of this is "The Night Before Christmas," in which phrases are built by two quick syllables followed by one long one. Inversely, dactylic meter is built with phrases consisting of one long syllable followed by two quick ones.
Write down the feelings you're trying to convey with this poem. This will be important for setting the scene for your poem.
Write a few lines of verse. Once you've begun, it's a matter of identifying effective rhymes for the most commonly used words. If you aim for line-ending sounds common in vocabulary, it will be easier to rhyme with them on subsequent lines.