Poetry lines do not end by accident. The poet determines the length of each line. With what ever else I say, you can break your lines where ever you wish, but line breaks are a poetic device why not use them for your advantage.
Before I get to deep into line breaks, I’ll mention line lengths. Short lines are faster and have more energy. Long lines are slower. The subject matter of the poem may dictate which you use. Though many poets tend to stay very much the same. It’s part of their voice. Line breaks are mini hesitations in a poem.
If you’re writing formed poetry, the line length is dictated by the form. Ex: Iambic pentameter – ten syllables, five stressed syllables, or ten iambs. Another common form/meter in modern poetry is syllabic poetry where each line has a set number of syllables.
There are two major types of line breaks: 1) end stopped – the line ends at the end of a sentence or phrase. Or another way of saying it is the line ends on punctuation. 2) enjambed – where the sentence or phrase is broke in the middle and the second part is on the next line. The most common line break even in enjambed is breaking on a normal breath pause. If you read the line aloud, a normal breath pause is where you pause to grab the next breath. Yes, another reader may breathe in a different place, but I think you’ll find most people are very consistent. But each poet has their own breaths. Whitman or Ginsberg were long winded. Kay Ryan is short winded. Look at their line lengths.
Another aspect of line breaks is visual appearance. How do you want the poem to look? For the last ten or so years, I’ve noticed poets accepting a varied line length. Okay. It does give the poem a more chaotic appearance. But that may be what the poet wants.
Even if you are writing in forms there are a few line breaks you want to avoid.
1) Try not to break on weak words, a, an, the, and, etc.
2) Don’t break in the middle of a prepositional phrase. Ex: “on the road” Breaking it “on/the road” isn’t gaining you anything.
3) Try not to always use end-stopped or enjambment. Vary it.
4) Don’t always break on the same part of speech.
The last words of lines are key words in the poem. They have to be, the readers eye will hesitate a millisecond longer on those words. As an example of what can be done with those key words, look at the first stanza of William Carlos William’s poem “This is Just to Say.” I’m not quoting the stanza but the last words of the lines are “eaten” “plums’ “in” “icebox.” That doesn’t follow through the rest of the poem, but WCW knew what he was doing with those line breaks. Yes, I know that’s a minimalist poem which makes it easier, but still…
Let line breaks work for you. If you use breath pauses to break lines and then have an unusual line break you’ve drawn attention to that spot in the poem. Save that for the turning or leaping place in the poem, the spot where you want the attention drawn.
Another trick with line breaks is called the ‘ambiguous’ line break. Here you manipulate the reader into believing one thing and then surprise them with a different meaning. Ex: ‘together in dream they are prone.” What does ‘prone’ mean to you. Likely that they are lying down. But what if the next line starts “to dance." Surprise! Be careful with ambiguous line breaks, they can be over done and start upsetting the reader. But they can work well at that special place in the poem. Don’t do it, just because you can.
Another aspect of line lengths is pacing. If the subject of the poem changes or the tension builds, it might help to shorten the lines. Thus increasing the tension more and speeding up the poem.
Remember, save unusual line breaks for effect. Use them to your advantage. Unusual line breaks create tension. Tension is necessary for a poem, but save the line breaks for effect in the places you want to change the tension level. Line breaks are a poetic device that can be very helpful in saying what the poem wants to say.