Narrative poems introduce a conflict, or problem. Poets build the conflict, which gives the piece its tension, through the use of poetic devices such as rhyme as well as plot elements such as climax. Writing a poem with a conflict requires thinking up a story and using poetic devices to convey the narrative.
Narrative poems recount a story, giving writers the opportunity to develop a conflict within them. In fact, any poem that tells a story is considered narrative poetry; specific forms depend on other elements. For example a narrative song with a sequence of rhymed, four-line stanzas makes a poem a ballad. Ballads usually relate heroic or tragic stories, though they can be comic. Poets build tension in the narrative by introducing a conflict and developing it throughout. For instance in the folk ballad "John Henry," the conflict is introduced in the first stanza with the main character's statement, "Hammer's going to be the death of me," foreshadowing the climax.
Before writing a specific type of poem, reading excellent examples of the form allows you to review techniques. Ernest Lawrence Thayer uses the ballad style to describe a baseball game in "Casey at the Bat." As with the folk ballad, the conflict is introduced at the outset, allowing the poet to develop it throughout the poem. Once inspired, you can begin to brainstorm ideas. Because the poem centers on a conflict, that is an effective place to start. Write down all the words and ideas associated with the conflict in a list or word web. While brainstorming, lines of poetry may already start forming on the paper. Take this to the drafting process.
Drafting a poem starts with putting pen to paper, or fingers to keyboard. For a narrative poem, sketch out the story, building to the conflict and resolution. Once the narrative is laid out, start crafting what makes the poem distinctive. If writing a ballad or other specific form, arrange the plot into the specified guidelines, rhyming and observing meter as necessary. For a free-form piece, evaluate your work for flow, word choice, sound and formatting. The goal is to build the tension surrounding the conflict, so you need to evaluate which poetic devices achieve that.
The first draft of any writing is not the completed piece. Writing needs revision, and this is especially true of poetry. You may want to ask others to review your work to offer suggestions for improvement. However, most of the work is up to you. Consider every word choice in the poem, asking yourself if it is the most powerful word, if a phrase conveys the sense you want, even if all the words are necessary. You may choose to return to the example poetry you read to help you perfect the craft. Seeing how professional writers use literary devices will help you apply that knowledge. Then assess whether you own use of poetic elements builds the tension of the poem's conflict.