Choose your subject. This is the topic you'll write about in your poem. The use of any poetic convention should evoke feeling appropriate to the subject. Pick your subject first; decide whether your poem will be about love, anger, beauty or something ordinary such as brushing your teeth.
Decide on the tone of the poem. The tone should be appropriate to the topic. Decide whether you want the tone to be upbeat and happy or slow and sad. The pace and tempo of the words you pick will affect the feel of the poem, so choose the tone before you start to write.
Decide on the length of your stanzas, which are units of text similar to paragraphs in prose. Stanzas can be short or long, from two lines to any larger number of lines, though most are between two and eight lines. Most rhyme schemes use an even number of lines for rhyming purposes, but a few, such as the limerick, use an odd number.
Decide on your rhyme scheme. A rhyme scheme is a design for the order of rhymes in a poem. Each rhyme will be denoted by a letter of the alphabet. For example "spout" and "out" rhyme, and "rain" and "again" rhyme (roughly), so the popular children's song "the itsy bitsy spider" gets the rhyme scheme aabb. Each stanza may have the same rhyme scheme or the rhyme scheme may vary throughout the structure of the poem.
Write your refrain first. The refrain is a stanza that repeats more than once throughout the poem for emphasis. A refrain should contain the core idea you want to express in the poem and be succinct but meaningful.
Write the text of your poem using the topic, tone and rhyme scheme you've selected. By using a refrain you are already using repetition, but you may choose to use this device in other ways throughout the piece by repeating sounds, words or even whole lines for emphasis and artistry.