It strikes me that there is a lot to do in this assignment and that it would be best to plunge straight into the action with a setting of the scene. Of course, to begin with, you have to place yourself somewhere in it if you're writing non-fiction. Let's imagine that you're a journalist, a former high school athlete yourself, going to visit a cheerleading practice in Galveston Texas.
"Hustle up ladies! Practice begins in two minutes!" A strong Texan accent moved faster than the gentle breeze through the early Galveston evening. The orange glow of sunset was giving way to the harsh fluorescence of the floodlights. A relieving coolness came with the breeze and with it a hint that the assault of a Texan summer was giving way to autumn and with it, the start of the football season. That brought back memories of my own playing days and memories of being on the edge of the varsity squad, watching the distant balletic beauty of the cheerleading squad and wanting to know more. As I waited for the young women to appear for training from their locker room, I was keen to know more than I had ever discovered when I was at school.
In that first paragraph, I was clear to try to bring in some dialogue, starting dramatically with some dialogue from the coach, in a dramatic manner to set the scene. I then broke out the sensory detail with the 'gentle breeze' and established the time of year quickly through the description of the breeze. The first paragraph also allowed a flashback that brought the story-teller in to the story, giving a motive for being there and then introduced a way into the story, giving the rationale for it, that the writer was there to investigate the lives of cheer-leaders whose activities he didn't fully understand.
I might then go on to give some dialogue with one of the cheerleaders after the practice is over, describing the busy nature of her day. I've deliberately set the story up with the reminiscences of the narrator and his idea of the 'balletic beauty' of the cheerleaders. He seems to see them as some sort of ideal. However, I might then go on to undermine the stereotype by revealing that things are rather different than the narrator imagines - something like this might be useful:
"I only started cheerleading when the gymnastics teacher left." Kerry told me after training. She was a tanned, athletic girl of 17, in her senior year at school and keen to let me know that cheerleading was know easy ride, as she packed her bag and books into the back of an old pickup truck in the school's parking lot, some two sweat-soaked hours later. "I'd trained since I was seven at gymnastics and the nearest club is on the other side of the city. It was either cheerleading for me or swim team and the swim team trains four hours a day. I'm trying to get in to Yale and, while I wanted to do something away from my studies, cheerleading provided the opportunity but let me keep at the books more. We're not all hairspray and lip gloss, y'know - this is hard work."
With this sort of writing, I would avoid any sort of dialogue that tried too hard to capture accents. Outside of one 'y'know' I've kept it direct so that a sense of the girl's determination shines through the dialogue. Incidental details in the description are also used to construct her character as a no-nonsense worker - the 'old pick-up truck' is used to give a sense of her as someone who is practical and no-nonsense, as is her willingness to confront stereotypes.
Perhaps, you could write this non-fiction account about cheerleading as a type of memoir in which you recall a friend's experiences when she tried out for a cheerleading team. Suppose that now she is a war veteran, who has lost a leg from a mine explosion in Iraq. and as an adult, you are re-united with this best friend from high school after she has been released from the hospital.
(you narrate) I thought it was going to be awkward when I saw Tracy after all these years, but when our eyes met, if was as if we were sixteen again. We hugged, we cried, we rocked back and forth, clutching each other fiercely as if our team had just won the conference! We laughed silly tears, grieving for our lost innocence; yet, peering through those tears at the future.
"Tracy, I found something at your old house on Lofter Street that you must have dropped when you moved. Your diary!"
"What?! Oh, my gosh; I can't believe it--Let me see! Did you read anything in it?"
"You know I did. And I cried tears of exultation, tears of loneliness for you, tears of sympathy. Trace, I felt as though you were there on the edge of the bed, talking to me."
[So, this diary and the memories of cheerleading unite you with your friend and you can describe how you recall the details of try-outs, how you felt, how proud your mothers were, the games you cheered at, life-lessons learned, etc.