That is, the word that corresponds in each case to A or B or C, etc, and appears at the end of a line, gets shifted around as the poem winds its way through the spiral. At the end of the six stanzas we have an Envoi, a kind of final greeting to the reader, which uses this pattern BE/DC/FA, squashing up the six key words into three lines.
It's rather difficult to explain, so here's a properly formed example from W H Auden called Paysage Moralisé. In this poem you can see how the key words at the end of the first six lines (valleys, mountains, water etc) wind their way around the poem.
Being keen to have a go at the Sestina, if only to say I've actually tried it, I produced the item below (notice I don't call it a poem). I discovered shortly after I started that I'd begun to rhyme the key words instead of actually re-using them; hence the variations. However I think the scheme is intact, and by the time I got to the envoi the words were back where they belonged again. The metre isn't consistent because it's not easy to concentrate on getting the metre right as well as all the other juggling of words, but since this is only a practice run, I'm not fussing about that too much.
I've written out the key words at the beginning, with their alphabetical symbol beside them. I haven't thoroughly checked but I think they're intact, at least in terms of rhyming with the original. The group of six letters are only at the side to give you an idea of where the key words/rhymes have gone to. I was originally going to use a bunch of words that I came across in relation to trailer hitches, but they proved a bit of an obstacle in the way of getting the Sestina off the ground. And anyway the 'poem' found its own way home.
A. Hitch, B. state, C. more, D. this, E. sans, F. did
To start a poem with a trailer hitch ABCDEF
Seems likely to put me in a state
Of dislocation, and furthermore
I haven’t a clue where I’m going with this
Which makes it a drive in the night sans
Headlights, which my brother-in-law did.
Well, now I’ve the problem that this grid FAEBDC
Called Sestina needs to work one stitch
At a time, like a number of hands
All pulling, as if pulling their weight,
But in fact, pulling that way and this,
Between table and chair, window and door.
And now I’ve made it a chore CFDABE,
Since I should stick to the grid
And not rhyme; how did I miss
That instruction? Surely some hitch
In my reading. So I’m now in a state
And reverting to form as a man’s
Wont to do if he just lets his glands ECBFAD
Rule him and acts like a boar
In a china shop throwing his weight
Everywhere, breaking this lid
And this plate, sending every which
Way and that crockery, with a hiss
And a roar, and unlikely to miss DEACFB
Any item he can lay his pig hands
On, or, with a whiskery twitch,
Like his cousin, the Minotaur,
(distant, I know) known to be hid-
den in his labyrinthic state
And rashly inclined to lie in wait BDFECA
For Heroes arriving in a bliss-
ful state of ignorance, fidd-
ling with their sword in their hands,
Relishing a fight and the gore
That would follow without hitch.
Brains lose on this, and furthermore,
Only Theseus did the deed without hitch.
[This post got picked up for the weekly highlights on the Frankfurt Book Fair 2012 - An Aotearoa Affair site. There are some interesting comments on the post there, including a note about Denise Duhamel's excellent Sestina: Delta Flight 659. Note how she plays with the form....]