• All lines are in dactylic meter. (DUH duh duh…)
• Line 1 is repetitive nonsense, rhymed if possible.
• Line 2 is a noun / noun phrase.
• All lines are 12 syllables, except for the fourth line in each stanza, which is 10 syllables.
• Lines 4 and 8 rhyme. (And 12, 16, and so on, in a longer poem.)
• In each pair of stanzas, at least one line—preferably line 6—is either two six-syllable words or one 12-syllable word.
• Examples here and here.

~ Alex Steelsmith