I usually talk about titles because a good title will make a poem stand out in a list of contents and could be the difference between the reader choosing to read your poem or the one on the page after yours.
However, a good ending will entice a reader to read and savour your poem again. A bad or underdeveloped ending will wreck the reader’s experience. What makes a good ending?
Have you wrapped up your poem like a ready-made kit?
If you’ve resolved every question, explained every image and tied up every loose end, your poem may feel complete but your reader will find it frustrating. What you’ve done is excluded the reader from interpreting your poem or failed to give them space to develop an emotional connection. Instead of giving your reader the kit and guide, you’ve already made-up the kit and left the reader thinking that was pretty but pointless.
Do you deliver the promise of your premise?
Poems have their own internal logic. If your poem is grounded in an urban landscape, suddenly veering off into fantasy for the final couplet will irritate. That doesn’t mean your urban landscape can’t have a surprising piece of architecture or that your poem can’t end with the narrator suddenly realising that s/he’s no longer on planet earth, but give your reader some clues earlier in the poem. Even in twist-in-the-tale stories, the clues to the twist were in the story if the reader was paying attention.
Have you over-explained?
If you cut the last two lines of your draft poem, does it still make sense? Trust the reader to understand your poem. If you feel the need to explain your ending, then your poem is not ready for publication. You can guide a reader towards the conclusion you’d like them to make, but you must allow for a reader to make a different interpretation.
Have you employed a Deus Ex Machina?
Readers feel cheated if the downtrodden hero/ine who never gambles discovers a winning lottery ticket or some wealthy relative (who hasn’t been mentioned in the story so far) turns up out of the blue or a fairy godmother waves a magic wand. Cinderella’s fairy godmother enabled her to go to the ball, but it was Cinderella herself who left her glass slipper behind so her prince could find her again.
In a poem, the narrator needs to resolve their own problem.
Is the form dictating your poem?
In an early draft, your poem might have looked like a sonnet but, if you’re struggling with the ending, it might be better to release it from a sonnet’s straitjacket.