I do keep forgetting to post this, and I've had it written for weeks. Poetry school continues! Tonight, I bring to you the sestina, possibly the most irritating form ever. It is a thirty-nine line poem. The first 36 lines are grouped in six stanzas of six lines each, then a three-line "tercet," also called the "envoy." Envoys are usually addressed directly to the person or thing that the rest of the poem is about--but not always.
The sestina becomes more difficult in that you choose six words as "ending" words for each line. You have to use them in a set sequence, like so:
123456--first stanza
615243--second stanza
364125
532614
451362
246531
And for the last three-line stanza, it's 2/5, 4/3, 6/1. Though you can do other forms, that's the one I used. And to make it harder on myself, I chose to make rhyming pairs of words. Most sestinas don't rhyme. It's just far too difficult, because you want to try to choose words that have more than one meaning, so you don't sound like you're repeating yourself. The best sestinas don't sound like they are using the same words over and over.