Discover the basics.
There are many ways to build a tercet. To quickly become proficient in the tercet, use the classic Italian form brought into the English language by Sir Thomas Wyatt five centuries ago. If you can write four or more stanzas with an aba-bcb-cdc-ded rhyming pattern, you can write a tercet in any of its other structured or free forms. This rhyming scheme offers plenty of room for movement and creativity but also requires deliberate word choice, especially end-line words, that can grow the poem.
When using the rhyme scheme of the terza rima, realize how well the interlocking rhymes tumble through the poem. Dante wrote an entire epic using this progressive rhyme scheme. While you probably shouldn’t detail your imaginative journey through hell as you familiarize yourself with this form, try creating your own short narrative using terza rima. You’ll quickly see how well the rhyme scheme pushes along the arc of your narrative.
This heartfelt phoenix that arose from the fires that devastated San Diego County in October 2007 demonstrates how the form can coax a poem along.
As fire scorches the farm, trees exploding in flame,
he remembers where they stood a week ago
and looks to find fault, but how can you blamethe winds of hearts when a new direction blows
out of nowhere, the cold hard slap of penance
striking his soul so hard, so suddenly he choseto unlock the cold heart that gave you not romance
but cuts and scrapes and tears and belittlements
that squashed your hopes and set you in trancewhen a new love blazed inside you, new movement
speeding along, leaping toward consummation until this brushfire
took away his trees, his barn, his pastheaven sent,for him, because it brought you back, inspired
to rebuild him by the awakened love swirling in your heart:
Now go rebuild him, precious one. Create new fire.
Poetry in motion.
Tercets live on rhythm. Be sure to capture the rhythm of your subject, and choose end-line words that give you options for later rhyming. This is especially crucial for the second line of each stanza, as the end-line word of this stanza will be rhymed with two end-line words of the next stanza. Then again, writing in terza rima (or in any verse structure, for that matter) should not be a linear process. You may find yourself writing through the rhyme and then reversing to change an end-line word that appears two lines before.
Also keep this in mind: tercets tumble from stanza to stanza, and your content should tumble along with the lines. Avoid using the "to be" family of passive verbs as much as possible, especially since they suggest stasis. Form your language to reflect the continual movement of this form. Subjects can be romantic, tragic, pensive, elegiac, or reflective; in other words, the scope of the human heart.