Basic elements.
Like other repeating-line poems, such as triolet and the villanelle, the keys to writing a rondeau are to generate a dynamic, catchy opening line, part of which will serve as the end-lines for the second and third stanzas; and to end that opening line with a word that has many rhymes. The overall rhyme scheme is aabba-aabR-aabbaR. The form itself combines a quintet, a quatrain, and a sestet, with lines ranging from eight to ten syllables.
Strong rhyme scheme.
A good example of a modern rondeau is W.E. Henley’s "In Rotten Row." The main difference between modern and early rondeaux lies in the affinity for rhyming off the opening line. Medieval and Renaissance poets focused on the force of their lines, while English poets developed rhythm.
Henley opens with a catchy line – the eventual refrain – and establishes a strong aabb rhyme scheme in the opening quatrain. He also works with eight-syllable lines, the traditional French form. "In Rotten Row" is an excellent hybrid of classic French and modern English rondeau style.
In Rotten Row a cigarette
I sat and smoked, with no regret
For all the tumult that had been.
The distances were still and green,
Paint the setting.
The opening rhyme scheme works through most of this quintet. Note the storytelling quality to the poem, and also how it rolls naturally into the truncated refrain just three words from the opening line. Use the second stanza to paint the setting and background of your rondeau.
And streaked with shadows cool and wet.
Two sweethearts on a bench were set,
Two birds among the bows were met;
So love and song were heard and seen
In Rotten Row.
Use the form’s flexibility.
The pastoral scene of the second stanza shifts to more action in the final sestet, driving toward a conclusion, similar to the villanelle form. Also, in the third line, Henley uses nine syllables. The rondeau gives you the flexibility to work with eight to ten syllables per line. Try to be consistent in your syllable counts per line, but if you need an extra syllable to deliver an effective line, take it. Also remember that the rondeau is rhythmic, fluid, and strong, and like a good pop song, it has a catchy refrain.
A horse or two there was to fret
The soundless sand; but work and debt,
Fair flowers and falling leaves between,
While clocks are chiming clear and keen,
A man may very well forget
In Rotten Row.