Like any story, a narrative essay relies on interesting characters. However, an essay does not give you the space of a short story to include all aspects of a character. Be sure to include character traits that are interesting and pertinent to the story, leaving out details that might distract the reader or derail your point. For example, it might be interesting to know that Aunt Penny climbed Mount Everest when she was 27. If the point of your essay simply requires her to be at your soccer game showing support, however, the Mount Everest part of her life should remain untold.
Dialogue is a good way to offer subtle details. Through a conversation between two characters, you can convey several things about who the characters are, what setting they are in or how the plot is advancing.
While you could simply say, "The sunset gave the boys hope that the summer heat would relent," using dialogue can make the point in a more interesting way:
"What time is it?"
"I don't know, but the sun is going down. Must be around 8."
"I never really liked sunsets. They remind me that another summer day is gone."
"Yeah, but the nights are cooler and I can breathe better after the sun's gone down."
"I guess. I still hate to see a day go, though."
Not only does this dialogue tell the reader that the sun is setting and they hope for a cooler evening, it also gives some insight into their characters. As long as these details are important to the point you are making, dialogue that reveals them will add interest to your essay.
The story in your narrative has to take place somewhere. You don't want to burden your reader with every minute detail of the setting, but you need to give some sense of place in order for it to take shape in the imagination. Well-drawn characters and expert dialogue will fall flat if your reader cannot picture where all of this is happening. Think carefully about the details you include here. If it is important to the point of your essay that the neighbor's house had torn window shades and an overgrown yard, include it. If the neighbor's house has little bearing on the point you're making, leave it out entirely.
When choosing verbs for your narrative, stay away from general words like "went" or "said." These are too easy and do little to create a picture of what is happening in your essay. Look for verbs that convey exactly the image you're trying to create. Consider the difference between the following sentences:
They went to the park.
They strolled to the park.
They marched to the park.
The first doesn't give any idea at all about the mood of the people on the way to the park. The second and third sentences reveal not only the destination but the attitudes of the characters who are on their way there.